CABAZON, Calif. (AP) — Two firefighting helicopters collided while responding to a blaze in Southern California, sending one to the ground in a crash that killed all three people on board.

The accident late Sunday afternoon in the desert about 85 miles east of Los Angeles involved a huge Sikorsky S-64E and a smaller Bell 407. The larger Sikorsky landed safely.

“Unfortunately, the second helicopter crashed and tragically all three members perished,” Cal Fire Southern Region Chief David Fulcher said at a news conference early Monday.

The Bell helicopter was being used for observation and coordination, Fulcher said. The Sikorsky can drop water or retardant on fires. Fulcher said he did not know whether it was loaded at the time of the crash.

The victims were Cal Fire Assistant Chief Josh Bischof, Cal Fire Capt. Tim Rodriguez, and contract pilot Tony Sousa, the firefighting agency said.

Cal Fire and Riverside County Fire Department resources had been dispatched to a structure fire near the intersection of Broadway Street and South Ronda Avenue in the community of Cabazon shortly after 6 p.m. That blaze spread into the surrounding vegetation and a full wildland fire dispatch was initiated, which included six airplanes and helicopters.

“That’s not an uncommon dispatch for a wildland fire, to send those resources,” Fulcher said.

Cal Fire said in a social media post at the time that the fire was burning “in light flashy fuels with a moderate rate of spread” and had spread over approximately 3 acres.

While battling the blaze, the two helicopters collided just before 7 p.m. The crash caused an additional 4-acre fire, which was extinguished.

“Although this was a tragic event, we are also thankful today that it wasn’t worse,” Fulcher said.

The sky was clear and there were breezy winds typical of the Cabazon area, said Capt. Richard Cordova, a Cal Fire public information officer for the region.

“They were good conditions to fly in,” he said.

The Bell crew’s mission was to tell helicopters where to make drops, working in conjunction with the crew of an airplane flying above all others, Cordova said. That aircrew’s role is called “air attack.”

“They kind of work together,” Cordova said. “The air attack is the main boss up in the sky and the helicopter coordinator assists with the air attack and helps out with the helicopters.”

The pilot of the crashed helicopter was flying under contract with the California Department of Forestry and Fire Protection. The Sikorsky and its two-person crew were also under contract.

Cal Fire operates its own fleet of about 60 aircraft but also contracts with commercial companies for additional helicopters and airplanes that are on standby at bases statewide.

Cordova said in-flight collisions are rare but have occurred during previous California wildfires. He recalled two instances over several decades but did not immediately have details.

The crash is being investigated by the National Transportation Safety Board.