A Somali man accused of leading mass executions and torturing people during the country’s bloody civil war in the 1980s has been quietly working as a security guard at a Washington, D.C., airport for the past six years – all while passing FBI and TSA checks.

Yusuf Abdi Ali, who is living in Alexandria, Va., is an employee at the Dulles International Airport, the Metropolitan Washington Airports Authority confirmed to Fox 5 on Wednesday.

The airport authority also said they are aware that Ali – who is now on administrative leave -- was named in a lawsuit filed by a human rights group in 2006 for crimes against humanity. The case has had numerous appeals and is now destined for the Supreme Court, CNN reported.

“The Metropolitan Washington Airports Authority maintains a contract with Master Security to provide unarmed security services,” said Rob Yingling, a spokesperson. “Master Security's employees are subject to the full, federally mandated vetting process in order to be approved for an airport badge, including a criminal history records check by the FBI and a security threat assessment by the TSA.”

Yingling said the authority has “verified that all of these processes were followed and approved in this instance.

“We have been informed by Master Security, which hired Mr. Ali, that he has been placed on administrative leave, and as a result his access to the airport has been withdrawn,” he added.

The company also said it was unaware of the pending litigation and is now reviewing the facts surrounding the case.

Officials told CNN that the U.S. government has been aware of Ali for years "based upon allegations that he had been involved in human rights violations,” but declined to elaborate.

"He oversaw some of the most incredible violence that you can imagine," Kathy Roberts, an attorney for the Center for Justice and Accountability (CJA), which is leading the civil lawsuit, told CNN. "He tortured people personally; he oversaw torture."

A government regime led by Mohamed Siad Barre took power and ruled with an iron fist after a coup in Somalia in 1969. Ali, who then served as a commander in the regime, is accused of terrorizing the once-dominant Isaaq clan in the country’s north.

"He tied [my brother] to military vehicle and dragged him behind. He said to us if you've got enough power, get him back," one villager said during a documentary that aired on CBC in 1992, according to CNN. "He shredded him into pieces. That's how he died."

Ali denies the accusations in the lawsuit, telling CNN that they are “baseless” and “false.”

"How dare anyone call him a war criminal," added his lawyer, Joseph Peter Drennan. “If he is indeed a war criminal, take him to The Hague. Or if he is a war criminal, take it up with the immigration authorities. Don't sue him in an American court... My client deserves to live in the U.S. just as any other legal permanent resident."

Ali entered the country on a visa through his wife, who became a U.S. citizen. She was found guilty of naturalization fraud in 2006 after claiming she was a refugee from the same Somalia clan Ali is accused of targeting.