Inquiry opens into vice, drugs cover-up Former US ambassador to Libya Christopher Stevens, who was killed in a rocket attack on his car in Benghazi. A US watchdog has launched an inquiry into claims that diplomatic security staff tried to cover up alleged sex-and-drugs charges against agents and diplomats. State Department diplomatic security agents are responsible for protecting 275 US embassies as well as the secretary of state - and the bureau last came under fire for last year's attack on the US mission in Benghazi, Libya. Now, in a new blow to the agency's credibility, a watchdog has called in outside law enforcement officers to investigate its procedures, amid claims it tried to hush up allegations of the use of prostitutes by agents and even an underground drug ring supplying contractors. An internal memo by the State Department's inspector-general found eight cases in which inquiries into alleged criminal activity by diplomatic security agents or contractors were influenced or halted, CBS television reported on Monday. They included allegations that security agents protecting former secretary of state Hillary Clinton "engaged prostitutes while on official trips in foreign countries," CBS said, quoting from the memo, a problem the report says was "endemic." It also revealed details of an alleged "underground drug ring" near the US embassy in Baghdad that was said to supply drugs to contractors working for diplomatic security. In one case, officials told the inspector-general they were told to stop investigating an American ambassador "who held a sensitive diplomatic post and was suspected of patronising prostitutes in a public park," CBS reported. State Department spokeswoman Jen Psaki did not deny any of the allegations contained in the CBS report, but refused to go into specifics. "We take allegations of misconduct seriously and we investigate thoroughly," Ms Psaki told reporters. All cases mentioned in the CBS report were thoroughly investigated or are under investigation. She dismissed the idea that the department would not hand over for prosecution any of its 70,000 staff if they were found to have engaged in criminal activity.