Investigators believe they found the general location where a large brush fire started on Big Pine Key that sparked last Sunday and continues to burn nearly a week later.
Monroe County Fire Rescue Chief James Callahan did not provide the exact location, but humans are likely behind the cause of the blaze that has charred close to 100 acres of the heavily wooded Lower Key, home of most of the nation's population of endangered key deer.
"We're very sure it didn't start by an electric generator, an electrical cord or a thunderstorm," Callahan said Thursday, when officials reported the fire was 40 percent contained.
But the exact cause is still under investigation by the state and county fire marshals.
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"It's very hard to pinpoint," he said.
Callahan's department handed over control of fighting the fire to the Florida Fire on Wednesday.
"It's always good to have the cavalry come in, and we can go back to focusing on structure fires, which is what we do," Callahan said.
The fire is burning around a populated area, but firefighters have been able to save all but one house and a garage, both of which went up in flames Sunday afternoon. There have been no reports of deaths or injuries to the public or firefighters throughout the situation, said Monroe County spokeswoman Cammy Clark.
Multiple departments battled the blaze when it flared up Sunday, including Miami-Dade Fire Rescue and firefighters from Naval Air Station Key West.
When asked whether more people left homeless after September's Hurricane Irma in the Lower Keys may be a contributing factor to the fire, Callahan said no, but the rustic lifestyle many on Big Pine have embraced for generations likely is.
"There's a pretty big population that live off the grid there," he said.
Many people live in makeshift homes, on boats and in the woods.
Scott Peterich, a spokesman for the Florida Forest Service, said the branches, leaves and other debris blown around by Irma, which hit Big Pine hard, is making the fire harder to extinguish.
"It's just a mess," he said.
Clark said given the size and complexity of the fire, and that the Keys is still in the dry season, mop-up operations could take weeks before it is completely knocked out.
"Residents and firefighters must remain vigilant and 'fire safe' as we remain in dry conditions," Clark said in a statement Thursday.