Congressman Gary Condit has taken and passed a lie detector test, according to a source close to the California Democrat.
It is unclear what questions were asked and who administered the test.
Police and Mr Condit's lawyers had been negotiating the limits of a test since Tuesday.
Police had been pressing for no restrictions on questions related to the disappearance of former federal intern Chandra Levy, while Mr Condit's lawyers said they wanted limitations.
The Condit source declined to provide any details about the test. Abbe Lowell, Mr Condit's attorney, plans a news conference.
Police say they have searched more than 70 vacant buildings in the US capital looking for Ms Levy, who was last seen April 30.
Capt Willie Smith said officers under his command were trying to get through 100 buildings in the neighbourhoods near Ms Levy's apartment. "We just want to make sure all the bases are covered," he said.
Police conceded it was a lack of good leads, rather than specific information, that led them to look at abandoned properties as places where someone could have left a body.
Police say they are pursuing four theories about Levy: She was murdered; she killed herself; she went into hiding or she has amnesia. However, police say they have all but ruled out suicide since so much time has passed and no body has been found.
Police have said repeatedly they do not consider Mr Condit a suspect in her disappearance. A police source has said the congressman acknowledged a romantic relationship with the former Bureau of Prisons intern, despite denials from his office.