Video shot by an onlooker at the airport showed a fireball exploding out of the damaged aircraft and recorded the startled cries of people watching.
The pilot and copilot escaped harm using a rope ladder on the right side of the aircraft, according to Mike Jachles of Broward Sheriff Fire Rescue. No members of the ground crews were hurt, he added.
The fire occurred after the plane's landing gear collapsed as it touched ground, the FAA said. The Boeing MD-10 was operating as Flight 910 from Memphis, Tennessee, where FedEx is based.
Most of the fire damage occurred on the plane's exterior near the left wing and engine, Jachles said. The interior of the plane appeared to be undamaged
The plane was carrying FedEx shipments and US Mail, he said.
FedEx Services Senior Communications Specialist Davina Cole said the company was cooperating with authorities. Boeing has not yet responded to a request for comment.
The Florida airport's south runway reopened for air traffic at 7 p.m., according to the airport's Twitter account. The north runway remains closed while the investigation of the FedEx plane fire continues.
The accident came hours after an American Airlines Boeing 767 was forced to abort its takeoff at Chicago's O'Hare International Airport because of an engine-related malfunction.