CNN  — 

Two single engine aircraft fighting the Bishop Fire in southern Nevada collided in mid-air around Thursday afternoon, according to the Federal Aviation Administration (FAA).

Both pilots were killed in the crash. Recovery operations are currently underway and initial notifications are still being made.

The Air Tractor AT8T aircraft were fighting the Bishop Fire near Caliente when the crash happened. Caliente is located about 150 miles northeast of Las Vegas.

Only a single pilot was aboard each aircraft at the time, the FAA said.

The FAA and National Transportation Safety Board (NTSB) will investigate the cause of the collision.

According to the Bureau of Land Management, the Bishop Fire grew to 7,000 acres overnight and is expected to be contained by August 5.

The cause of the fire is unknown.