Two San Francisco paramedics are under fire after one was accused of having sex in a city-owned ambulance while on duty, and other of covering for him, sources say.

The men work out of Station 49 in the Bayview District and took an ambulance out for a drive, sources say. They are then suspected of picking up a woman, who had sex with one of the men, while the other one drove, according to sources.

An investigation, which was launched after someone filed a formal complaint with the Fire Department, is underway to figure out exactly what happened. It remains unclear who complained.

At least one of the paramedics could lose his job over the allegations, sources say.

On Friday, a Fire Department spokesperson declined to comment on personnel matters. NBC Bay Area has reached out to the accused firefighters and the union, but has not heard back.