The US Federal Bureau of Investigation (FBI) said on Monday it has started using polygraph tests to aid investigations aimed at identifying the source of leaks emanating from within the law enforcement agency.

“We can confirm the FBI has begun administering polygraph tests to identify the source of information leaks within the bureau,” the bureau’s public affairs office told Reuters in a statement.

Donald Trump’s administration has been cracking down on people who leak information to journalists since he returned to office in January.

Last week, the Republican US Department of Justice made it easier to subpoena records and testimony from journalists.