Robbers caught a Las Vegas corrections officer with his pants down last month having sex with an underage prostitute, authorities said Wednesday.

They were able to make off not only with his uniform but also his handgun, badge and Metropolitan Police Department ID.

In addition to taking everything needed to impersonate an officer, they also stole the man's wallet and his 1999 white Lexus sedan.

The officer, 28-year-old Walter Washington, initially lied to police about the robbery, saying he was attacked about 1 a.m. Oct. 25 by two Hispanic men who carjacked him after he bought a soda at a 7-Eleven near Atlantic and Fremont streets.

But police were later able to determine that Washington was robbed while he was having sex in his car in an alley behind the convenience store -- after he and the girl bought condoms at the store, said Lt. Ted Snodgrass of the Las Vegas police's robbery unit. Washington had met the teen at a nearby Denny's, Snodgrass said.

Washington is now the subject of an internal affairs investigation, said Las Vegas police Deputy Chief Mike Ault. He wouldn't discuss the details of the investigation.

Washington has been with the department since January 2001 and is on paid administrative leave pending the outcome of the investigation, said officer Bill Cassell, a department spokesman.

Washington initially told police that he was driving away from the store when one of the suspects jumped in front of the car, pulled the door open, hit him in the head with a flashlight and ordered him to take off his pants and shoes, according to a police report. Washington told police he tried to run away, but the robbers caught up with him, pointed a gun at him and ordered him to give up the car keys he had in his hands.

But when he was interviewed later by robbery detectives, Washington admitted he was with a prostitute when he was robbed. Detectives also watched surveillance footage from the 7-Eleven on the morning of the incident and saw Washington with the teen, Snodgrass said.

Police said that immediately after the robbery, Washington ran to a nearby motel and called a friend, fellow corrections officer James Jackson, because he needed clothes. They then drove to Jackson's house to call police, according to the report.

Police weren't certain whether the prostitute was involved in the robbery, because she had sex with Washington. Normally in "trick rolls," the "john" is robbed before any sex takes place, police said.

But police "are leaning toward this being an organized" trick roll, Snodgrass said, because the two robbers are believed to be from the Balkans and the girl was born in Romania. The teen is a former foster child, a source familiar with the investigation said.

She had previously been booked into the Clark County Detention Center under a false name as an adult. But police discovered who she was after checking various records, Snodgrass said.

No arrests had been made in the case as of Wednesday night.

Cassell said no criminal charges had been filed against Washington because the matter was still under investigation.

Snodgrass said Washington "is not being treated any differently than anyone else."

"The guy is still a victim, whether people think so or not," Snodgrass said.