SYDNEY - A drunken bus-load of elite Australian police officers were caught with their pants down when a motorist reported a "nudie run" at a traffic intersection, officials said Tuesday.

The men, members of the explosives and hostage negotiation squad, were using an unmarked police bus to travel from a stag party cruise on Sunday afternoon, Commissioner Bob Atkinson said.

They stopped at least four times at traffic lights across Brisbane, the state capital of Queensland, to run naked around the bus in a prank known as a "Chinese Fire Drill".

At least one of the officers was on duty, in a scandal which comes after a Queensland policeman was suspended for allegedly urinating in public and another over an unauthorised high-speed pursuit.

"It's a nightmare in the sense that you just hope there's nothing else coming," Atkinson said. "There is no excuse for this."

Atkinson acknowledged their remorse but said it was not an appropriate way to let off steam, particularly not using a police vehicle.

They could be charged with wilful exposure and public nuisance, and face disciplinary action ranging from a caution to the sack.

Queensland's Police Union (QPU) said the highly trained officers were on call 24 hours a day and rarely drank alcohol, so their behaviour was "completely out of character".

"However, I think that many Australians can relate to things that can occur on bucks or hens celebrations," said QPU president Ian Leavers.

"People often behave in a way that they wouldn't normally whilst on a bucks celebration, and that's what happened in this case."