Air accident investigators have begun an inquiry into a fatal mid-air crash between two helicopters in Arizona, in the US.
Four people died after two helicopters, owned by rival television channels ABC15 and 3TV, collided while covering a car chase in Phoenix.
The helicopters crashed to the ground in a blaze of fire and smoke.
One pilot and one cameraman from each aircraft died in the crash.
The crews had been filming footage of a truck that was being pursued by police on the ground.
The driver involved in the car chase was later detained by police.
