MEXICO CITY -- U.S. officials say the U.S. knew that Mexican marines had killed the head of the widely feared Zetas drug cartel before the body was stolen in a pre-dawn raid from a Mexican funeral home.

One official says the U.S. independently verified the identity of Zeta founder and leader Heriberto Lazcano, killed in a shootout Sunday afternoon in a northern Mexican town, before his body was stolen at gunpoint early Monday.

The account throws into question the Mexican navy's insistence that marines left Lazcano's body unguarded because they thought they had killed a common criminal. They only later discovered from finger prints on the body that it was Lazcano, the navy said.

Both U.S. officials spoke on condition of anonymity because they were not authorized to speak to the press.

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  • The Zetas were formed in the late 1990s by 14 soldiers who deserted from army special forces to work as muscle for the Gulf Cartel. Their name comes from a military radio code. <em>Caption: Weapons seized during a police and military raid are displayed in Coban, province of Alta Verapaz, Guatemala, Tuesday, Dec. 21, 2010. (AP Photo/Rodrigo Abd)</em>

  • The Zetas split from their former bosses in early 2010, waging an aggressive drive to expand their territory. They recruited from Guatemala and Texas, co-opting existing gangs to do their dirty work, while diversifying their criminal enterprises from drugs into kidnapping, extortion and even music piracy. <em>Caption: Guatemalan special forces soldiers known as a "Kaibiles" partake in training in this Feb. 12, 2005 photo at a military base in Guatemala City, Guatemala. (AP Photo/Moises Castillo, file)</em>

  • The Zetas are known for their brutality and are blamed for some of the worst atrocities in Mexico's drug war, including the murder of 72 migrants and the burning of a casino that claimed 52 lives. In May, they allegedly dumped the headless and limbless torsos of 49 victims near the city of Monterrey. <em>Caption: Clandestine graves are seen in the backyard of an alleged drug traffickers' safe house where six bodies were found during the past weekend in Tlajomulco de Zuniga outskirts Guadalajara City, Mexico, Monday, March 20 2006. (AP Photo/Guillermo Arias)</em>

  • Mexican officials say the Zetas are the largest of the cartels and could have as many as 10,000 members across Mexico, Central America and the United States. <em>Caption: Alleged kidnappers from a criminal band known as "Los Zetas", are presented to the media at the Federal police headquarters in Mexico City, Thursday, March 5, 2009. (AP Photo/Alexandre Meneghini)</em>

  • The Zetas gang had recently appeared to be rupturing due to disputes among leading gang members. A longstanding rivalry between Lazcano, also know as "The Executioner," and his deputy, Miguel Trevino, alias "Z-40," exploded into violence in recent months. <em>Caption: This undated image taken from the Mexican Attorney General's Office rewards program website on Aug. 23, 2012, shows the alleged leader of Zetas cartel, Miguel Angel Trevino Morales, alias “Z-40.” (AP Photo/Mexican Attorney General's Office website)</em>