Two single-engine planes collided in midair Thursday afternoon during firefighting activities in southeastern Nevada, according to reports.
Both pilots were killed in the crash and a recovery effort was underway, FOX 5 of Las Vegas reported.
"We offer our sincere condolences to the families of the two pilots and to all those working with the BLM Nevada Ely District," BLM Nevada State Director Jon Raby told the station.
"BLM" refers to the state Bureau of Land Management.
A Federal Aviation Administration (FAA) spokeswoman told Fox News the accident occurred while the planes were fighting the Bishop Fire near Caliente, Nev., around 1 p.m.
The FAA and the National Transportation Safety Board (NTSB) will lead the investigation, and the NTSB will determine the probable cause of the crash.
Investigators have yet to verify the aircraft tail numbers at the crash site.
Each plane had only the pilot aboard, authorities said.
Tanker planes can carry as much as 800 gallons of fire retardant and can provide service to areas that are unreachable for large tankers, FOX 5 reported.