A firefighting helicopter crashed, killing all three crew members, after it collided with a second helicopter while battling a blaze in southern California on Sunday, fire officials said.

Riverside County firefighters were called to the scene of a structure fire in Cabazon at about 6 p.m. on Sunday and they soon noticed that the blaze had moved into the nearby grass, Cal Fire Southern Region Chief David Fulcher said.

Cal Fire helicopters and planes were called in to help extinguish the blaze, he said.

"While engaged in the firefight, two helicopters collided," Fulcher said in a midnight press briefing. "The first helicopter was able to land safely nearby. Unfortunately, the second helicopter crashed and, tragically, all three members perished."

The crew included a Cal Fire division chief and a captain, along with a pilot, who was contracted by the department, Fulcher said.

The crash happened near Pipeline Road and Apache Trail, the Riverside County Sheriff's office said in a statement, adding that the National Transportation Safety Board would be taking over the investigation.

Both helicopters were contracted by Cal Fire and arrived at the scene with different objectives, fire officials said.

The helicopter which was able to safely land was a Sikorsky Skycrane, a type that carries retardant or water that's dropped on a blaze, Fulcher said. The one that crashed was a Bell helicopter, used for observation while fighting fires.

The crash caused an additional four-acre fire, which was then extinguished, Fulcher said.

This is a developing story. Check back for updates.