Firefighters in Greater Manchester will be "embarrassed at best" after a picture emerged apparently showing a woman having sex in one of their appliances.
Greater Manchester Fire and Rescue (GMFRS) is investigating the "inappropriate images" which were published in the Sun on Wednesday.
The paper claimed the picture was "one of a series of explicit images posted on a swinger's website" from a man who said he worked as a firefighter.
In the published image, fire equipment can be seen inside the engine, which bears the website address of the service.
A spokesman said: "I cannot believe we're still seeing highly inappropriate images like this in the fire and rescue service in 2017. It's not who we are.
"Firefighters in GMFRS are hard-working and proud to serve their communities. They are professional and diligent. Crew will be embarrassed by this at best.
"Most people will be furious at the suggestion this is acceptable or a reflection of how we behave. It isn't.
"We'll do everything we can to find out about how this picture was made and who was involved. There is no place for this in our organisation."