A Metro Transit Police officer was arrested yesterday and charged with rape in an incident that allegedly occurred while he was in uniform, the Montgomery County police said.

County police said Darren Michael Way, 31, of Broadwater Way in Gaithersburg was being held without bond. A Metro spokeswoman said Way was dismissed Friday after about 21/2 years on the force.

His accuser was a 33-year-old woman from Silver Spring who advertised as an escort or prostitute, the county police said.

In a statement, Montgomery police said that after making an appointment by phone about 2:30 a.m. June 16 or 17, the woman answered a knock at her door to find a uniformed police officer.

The officer drew his gun, the statement said, and "demanded her services."

According to the statement, the woman complied and asked for payment.

"She was told," the police said, "that she was not going to be paid."

Detectives learned of the alleged incident about two weeks later. A telephone number found in the woman's cell phone figured in the investigation, police said.

The county police said that on the night of the alleged offense, Way was on duty in the District "near the location of the incident."

Metro spokeswoman Candace Smith said Way had been a patrol officer, but she could not immediately say where he was assigned that night.

Smith said Way was placed on administrative leave when Metro learned of the investigation. He is the third officer arrested in the 30-year history of the 400-member force, she said.