By Jared Taylor

BROWNSVILLE, Texas, June 29 (Reuters) - The mother of a U.S. federal agent shot to death in Mexico last year said Friday she believes the weapon used to kill her son came from a botched federal gun-running operation that put firearms into the hands of Mexican drug cartels - a charge denied by the government.

U.S. Immigration and Customs Enforcement special agent Jaime Zapata, who was raised in Brownsville, was shot to death while traveling in a vehicle in Mexico in February 2011 in an attack that wounded his colleague, agent Victor Avila.

The agents were driving in an armored vehicle on a highway to Mexico City from San Luis Potosi when they were ambushed in broad daylight by suspected drug gang members. Two guns used in the attack were later recovered and traced back to Texas.

Speaking at a news conference in Brownsville on Friday, Zapata's mother, Mary, said she believed the weapons were allowed to slip into Mexico as part of the controversial "Operation Fast and Furious" run by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF.

"It's sad to know our own government allowed those weapons to get into the hands of the cartels and to know we still have agents in Mexico who are exposed," she told Reuters after a news conference held jointly with Avila's family.

An ATF spokeswoman said Friday that the weapons used in the attack on Zapata and Avila were not linked to Fast and Furious. The U.S. Justice Department declined to comment.

Fast and Furious was a federal law enforcement program intended to track weapons sold in Arizona that were suspected of being transported to Mexico for use by violent drug cartels.

Republicans accuse the Obama administration of allowing guns to enter Mexico that were used in at least one case to kill a U.S. official - Border Patrol agent Brian Terry, who was shot dead during a confrontation with suspected border bandits in Arizona in December 2010.

Following Zapata's murder, the ATF traced the assault rifle used in the shooting to a purchase made by three Dallas-area men, who were sentenced in February for buying a dozen firearms transferred to the Zetas, one of Mexico's most feared drug gangs.

Lawyers representing Avila and the Zapata family filed three claims June 14 against federal agencies, demanding more than $62 million in damages in what one of the lawyers said was a precursor to a federal suit.

Mary Zapata said federal officials have not shared any details surrounding her son's death beyond what has already been reported in the media.

"It has been very difficult," she said. "I feel like I owe my son justice and we haven't gotten it."

Avila has recovered from the gunshot wounds to his leg, but remains on leave from ICE as he continues to recover emotionally, said his sister and lawyer, Magdalena Villalobos.

"There's not a day that goes by - not a moment - that this isn't on his mind," she said. "It's been very difficult."

An alleged member of the Zetas cartel, Julian Zapata Espinoza, was subsequently arrested and extradited to the United States last December.

Furor over Operation Fast and Furious has drawn intense scrutiny from Republicans in Congress, and led to calls for Attorney General Eric Holder, who heads up the Justice Department, to step down.

Holder was cited on Thursday for contempt of Congress by the Republican-led House of Representatives. The Justice Department, which he heads, said Friday it would not prosecute him. (Editing by Corrie MacLaggan and Tim Gaynor)

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  • From left, House Minority Whip Steny Hoyer of Md., Rep. Maxine Waters, D-Calif., Rep. John Lewis, D-Ga., Rep, Charles Rangel, D-N.Y., and House Minority Leader Nancy Pelosi of Calif., right, and many House Democrats walk out of the Capitol during the vote to hold Attorney General Eric Holder in contempt, Thursday, June 28, 2012, on Capitol Hill in Washington. (AP Photo/J. Scott Applewhite)

  • House Oversight and Government Reform Committee Chairman Rep. Darrell Issa, R-Calif., left, and the committee's ranking Democrat Rep. Elijah Cummings, D-Md., go to the House Rules Committee, on Capitol Hill in Washington, Wednesday, June 27, 2012, to argue procedures as the House of Representatives prepares to vote on whether Attorney General Eric Holder is in contempt of Congress because he has refused to give the Oversight Committee all the documents it wants related to Operation Fast and Furious, the flawed gun-smuggling probe involving Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • Rep. Carolyn Maloney, D-N.Y., left, stretches out her hand to get the attention of Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, as the panel considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, sits between them. (AP Photo/J. Scott Applewhite)

  • WASHINGTON, DC - JUNE 20: House Oversight and Government Reform Chairman Darrell Issa (R-CA) (C) talks with raking member U.S. Rep. Elijah Cummings (D-MD) (L) during a mark up hearing on Capitol Hill June 20, 2012 in Washington, DC. Issa and the committee Republicans called the hearing to vote on holding U.S. Attorney General Eric Holder in contempt of Congress for refusing to hand over documents the GOP says are key to their investigation into the failed Fast and Furious operation. Before the start of the hearing, the White House asserted the documents are protected by executive privilidge. (Photo by Chip Somodevilla/Getty Images)

  • Rep. Darrell Issa, R-Calif., center, chairman of the House Oversight and Government Reform Committee, confers with an aide as the panel considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, second from left, speaks with Rep. Carolyn Maloney, D-N.Y., who authored an amendment in support of Holder. In a showdown with President Barack Obama's administration, House Republicans had pressed for more Justice Department documents on the flawed gun-smuggling probe known as Operation Fast and Furious that resulted in hundreds of guns illicitly purchased in Arizona gun shops winding up in the hands of Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • Rep. Jason Chaffetz, R-Utah, center, debates Rep. Stephen Lynch, D-Mass., as the House Oversight and Government Reform Committee considers a vote to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. (AP Photo/J. Scott Applewhite)

  • The House Oversight and Government Reform Committee, led by Chairman Darrell Issa, R-Calif., right, considers whether to hold Attorney General Eric Holder in contempt of Congress, on Capitol Hill in Washington, Wednesday, June 20, 2012. Rep. Elijah Cummings, D-Md., the ranking member, speaks at left. In a showdown with President Barack Obama's administration, House Republicans are pressing for more Justice Department documents on the flawed gun-smuggling probe known as Operation Fast and Furious that resulted in hundreds of guns illicitly purchased in Arizona gun shops winding up in the hands of Mexican drug cartels. (AP Photo/J. Scott Applewhite)

  • WASHINGTON, DC - JUNE 20: House Oversight and Government Reform raking member U.S. Rep. Elijah Cummings (D-MD) (R) hears from U.S. Rep. Dennis Kucinich (D-OH) during a mark up hearing with June 20, 2012 in Washington, DC. Chairman Darrell Issa (R-CA) and the committee Republicans called the hearing to vote on holding U.S. Attorney General Eric Holder in contempt of Congress for refusing to hand over documents the GOP says are key to their investigation into the failed Fast and Furious operation. Before the start of the hearing, the White House asserted the documents are protected by executive privilidge. (Photo by Chip Somodevilla/Getty Images)

  • Attorney General Eric holder speaks to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Rep. Issa met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs.(AP Photo/Susan Walsh)

  • Rep. Darrell Issa, R-Calif., speaks to reporters following his meeting with Attorney General Eric Holder on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Issa met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs. (AP Photo/Susan Walsh)

  • Attorney General Eric Holder speaks to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. Holder wants a House panel to drop plans to try to hold him in contempt of Congress, and the panel's chairman wants more Justice Department documents regarding Operation Fast and Furious, a flawed gun-smuggling probe in Arizona. Holder and Rep. Darrell Issa, a California Republican, met in an effort to resolve their dispute over the investigation of Fast and Furious by the House Oversight and Government Reform Committee that Issa chairs. (AP Photo/Susan Walsh)

  • Attorney General Eric Holder walks through Statuary Hall to speak to reporters following his meeting on Capitol Hill in Washington, Tuesday, June 19, 2012. (AP Photo/Susan Walsh)

  • FILE -In this Dec. 8, 2011 file photo, House Judiciary Committee member Rep. Darrell Issa, R-Calif., left, shakes hands with Attorney General Eric Holder on Capitol Hill in Washington. Holder is proposing to meet with Issa by Monday to settle a dispute over Justice Department documents the congressman is demanding on a flawed gun-smuggling probe. (AP Photo/Susan Walsh, File)

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