These pranksters are real ball busters.

Two Detroit city workers on a bathroom break were reportedly injured when firecrackers exploded as they sat down on toilets inside their fire truck repair shop Wednesday.

The stunt left one of the men with injuries to his leg and scrotum, according to the Detroit Metro Times.

The victims are employees of the city’s General Services Department, an agency that repairs city fire trucks and other equipment, the report said.

The city’s deputy fire commissioner, Dave Fornell, told the paper the incident “was a prank gone bad.”

President of the Detroit Fire Fighters Association, Mike Nevin, insisted his members were not to blame.

“This is an absolute embarrassment,” Nevin told the paper. “It is important for the public to know that no DFFA employees were involved in this incident.”

Detroit police are working to determine who’s behind the prank.