"The FBI was present in the vicinity of Windridge Drive and Estate Drive in Laredo conducting court-authorized law enforcement activity," the FBI said in a statement.

"The FBI cannot provide further comment on an ongoing investigation."

A spokesperson for Cuellar told CNN that "Congressman Cuellar will fully cooperate in any investigation.

He is committed to ensuring that justice and the law are upheld."

Cuellar, a moderate Democrat, has served in Texas's 28th Congressional District since 2005.

The news was first reported by The Monitor newspaper.