The federal Bureau of Alcohol, Tobacco, Firearms and Explosives—or ATF—is under the gun yet again.

Mexican police recently conducted a raid in Ciudad Juarez, a hotspot for the drug trade, and they swept up a cache of weapons. Among that cache? At least five assault rifles linked to a secretive anti-smuggling operation by ATF, reported the Wall Street Journal. Critics and ATF whistleblowers have for months claimed that the operation—dubbed “Fast and Furious”—has backfired.

The questions about Fast and Furious were first reported by CBS News and iWatch in March, and noted by us at the time. According to whistleblower accounts, ATF supervisors told agents not to seize weapons sold to suspected low-level smugglers but to track them instead, in hopes of dismantling drug rings and netting ringleaders.

The whistleblowers claim this strategy allowed thousands of weapons to pass into Mexico and fall into the hands of criminals. Prior to the latest discovery of these five weapons, other guns that the ATF had flagged as suspect had been linked to the killing of U.S. Border Patrol agents.

The Justice Department—which oversees ATF—has denied some of the specifics about the Fast and Furious operation, though many of the details are still sketchy.

The Journal notes that Attorney General Eric Holder told lawmakers last month that the Department has barred ATF and other agencies from using such tactics, and its policy is to stop guns from being smuggled to Mexico. As we’ve noted, the Justice Department had some more specific denials in March. Back then, Justice sent a letter to Sen. Chuck Grassley, stating that ATF “makes every effort” to prevent arms smuggling into Mexico and has never sanctioned or "knowingly allowed the sale of assault weapons to a straw purchaser who then transported them into Mexico."

Since questions about the program were first reported, the Obama administration has distanced itself from the whole operation. "We don’t have all the facts," President Obama told a Univision reporter in March. “I did not authorize it. Eric Holder, the attorney general, did not authorize it. He’s been very clear that our policy is to catch gunrunners and put them into jail.”

The Justice Department’s inspector general is currently investigating. Several Republican lawmakers—namely, Sen. Chuck Grassley and Rep. Darrell Issa—have also launched Congressional probes. Issa has subpoenaed documents.