A firefighting helicopter crashed during a training exercise in Florida on Tuesday — and all four people aboard are feared dead, authorities said.

The chopper went down in a marsh near Leesburg International Airport in Lake County at about 4 p.m., according to the Federal Aviation Administration.

Rescue crews confirmed one death and have so far not been able to locate any survivors.

“The crash appears to be a total loss,” Leesburg Fire Rescue said in a Facebook post.

A photo posted by the fire department shows thick black smoke billowing into the air from a forested area.

The FAA and National Transportation Safety Board will investigate the wreck.

With Post wires