WASHINGTON -- Congressional Republicans went hunting for controversy over last year's terrorist attack in Benghazi, Libya, in an unlikely place on Wednesday: the Senate confirmation hearing for Treasury secretary nominee Jack Lew.

Lew, President Barack Obama's chief of staff since January 2012, was grilled by Sen. Richard Burr (R-N.C.) about who briefed the president during the hours the attack on the U.S. diplomatic mission in Benghazi was taking place. Four Americans were killed in the Sept. 11 assault, including Christopher Stevens, the U.S. ambassador to Libya.

The question of President Barack Obama's whereabouts during the seven-hour siege resurfaced as a focal point of Republican concern during a hearing last week when outgoing Defense Secretary Leon Panetta said he did not brief the president after an early evening meeting about the attack.

One recurring conspiracy theory holds that Obama signed off for the night while the assault raged, motivated in part by a desire to sleep well before a fundraiser the next day in Las Vegas.

Panetta last week insisted that even if he did not personally speak with the president, the White House was in regular contact with national security officials throughout the attack. "The president is well-informed about what is going on, make no mistake about it," Panetta said amid contentious questioning from Sen. Lindsey Graham (R-S.C.).

Burr, questioning Lew before the Senate Finance Committee on Wednesday, suggested no one knows who kept Obama informed -- if anyone did -- as the attacked progressed.

Ticking off a list of officials who had previously said they did not brief the president, Burr said, "Now, we’ve eliminated a lot of people who had contacts within the intelligence community that knew firsthand what was going on in Benghazi. Let me ask you again: Who briefed the president on actually what was happening throughout this seven-hour period?"

Lew responded that while he was one of several people who met with Obama about the attacks, "intelligence community was in close touch with the White House, with the national security team on a near-constant basis."

In fact, White House officials have previously said that Obama was informed of the attack by National Security Advisor Tom Donilon, and was "kept apprised throughout the evening and then again Wednesday morning."

In her own Benghazi testimony before a Senate committee last month, outgoing Secretary of State Hillary Clinton said she spoke with the president late in the evening, and that she and her staff "kept talking with everyone during the night."

Another clue to the seemingly straightforward question of who actually spoke to the president may be found on the White House official Flickr feed, which includes a photograph from the night of the attack showing Obama being briefed by his deputy national security adviser, Denis McDonough, while Lew, Donilon, and Vice President Joe Biden look on.

The caption says the officials are giving Obama updates on "the situation in the Middle East and North Africa."

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  • A burnt out vehicle sits smoldering in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A broken window after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • The U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A burnt car is seen after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Soot and debris spills out of the U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man looks at documents at the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. The graffiti reads, "no God but God," " God is great," and "Muhammad is the Prophet." (AP Photo/Ibrahim Alaguri)

  • A man walks on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Glass, debris and overturned furniture are strewn inside a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man walks through a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A vehicle and the surrounding area are engulfed in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • An armed man waves his rifle as buildings and cars are engulfed in flames after being set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle burns after it was set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle sits smoldering in flames after being set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle and surrounding buildings smolder after they were set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • LIBYA CONSULATE

    Map locates Benghazi, Libya, where the U.S. ambassador to Libya and three other Americans were killed in an attack