Three people have died following a helicopter crash during a firefighting mission in the US state of California.

The incident happened on Sunday evening after fire crews were called to a blaze near Cabazon, Riverside County.

The two helicopters collided, with one then landing safely and the second crashing into the ground, killing everyone on board.

An investigation has been launched into the cause of the crash by the National Transportation Safety Board.

The victims were identified as a fire captain and division chief from the state’s Department of Forestry and Fire Protection (Cal Fire), as well as a contracted pilot. They have not been named.

David Fulcher, southern region chief for Cal Fire, described the incident as a “tragic loss”.

“We have lost three great individuals. Three fathers, three husbands, three friends, three sons,” he said.

“Daughters have lost their fathers, sons have lost their fathers”.

Mr Fulcher told a press conference the fire initially broke out in a building but later grew into a vegetation fire covering four acres (4,000 sq metres) that was eventually put out.

The helicopter that crashed was being used for observation, while the one that landed safely was helping to put out the fire. Both had been contracted to Cal Fire.