Weapons involved in the infamous U.S. firearms operation called "Fast and Furious" have been linked to Mexican drug kingpin Joaquín "El Chapo" Guzmán and the killings of three Mexican police officers.

"Fast and Furious" Weapons Linked to El Chapo

According to a Justice Department summary issued on Tuesday, agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) have connected a rifle recovered at El Chapo's former hideout before he was taken into custody in January. Assistant Attorney General Peter J. Kadzik confirmed that a .50-caliber rifle found at Guzmán's Los Mochis residence was associated with the "Fast and Furious" operation.

In a statement, Kadzik wrote that the rifle was purchased in July 2010 by a person identified as a subject of the operation. He added that the ATF had not connected the weapon to other crimes.

Under the "Fast and Furious" operation, which ran from 2006 to 2011, ATF agents allowed narcotics traffickers to illegally buy and sell thousands of firearms so that they could track the weapons back to Mexican drug cartels. However, the controversial operation backfired after it was discovered that some of the guns were being used to kill innocent people along the Arizona-Mexico border, including U.S. Border Patrol agent Brian Terry in 2010. The flawed operation also led to a congressional inquiry and the ouster of the U.S. attorney in Phoenix who approved it.

"Fast and Furious" Weapons Linked to Police Killings

It was also recently discovered that another weapon linked to the botched investigation was used last year in a deadly shootout that left three Mexican police officers dead.

A Justice Department summary provided to two Republican congressional committee chairmen Tuesday found that a WASR-10 rifle, which was purchased in a November 2009 transaction as part of the flawed federal gun trafficking operation, was one of three rifles fired in the July 27 assault in the town of Valle de Zaragoza.

"ATF and the (Justice) Department deeply regret that firearms associated with Operation Fast and Furious have been used by criminals in the commission of violent crimes, particularly crimes resulting the death of civilians and law enforcement officers,'' Kadzik said Tuesday in a letter to Senate Judiciary Committee Chairman Charles Grassley of Iowa and House Oversight and Government Reform Chairman Jason Chaffetz of Utah.

"ATF accepts full responsibility for the flawed execution of Fast and Furious, and will continue to support Mexican law enforcement in efforts to recover and identify associated firearms," he added.

The Department of Justice letter goes on to state that 885 firearms purchased by targets of the ATF operation have been recovered as of January of this year. Of those weapons, 415 were found in the U.S., while 470 "appear to have been recovered in Mexico.''