A woman was killed Wednesday morning when fire ravaged a Buford home and caused a floor to collapse into the basement.

Gwinnett County fire officials said they found the victim’s body in the basement. Authorities later determined that’s where the fire started, though the exact cause remains under investigation.

The blaze in the 100 block of Kennesaw Street had “a significant head start” on fire crews, department Lt. Donald Strother told Channel 2 Action News at the scene.

The first crews to arrive around 3 a.m. found flames shooting from the side and blowing out of the rear windows of the house. A witness who had called 911 to report the fire told crews a woman was in the basement and they weren’t sure if she could get out.

The trapped woman, identified in a GoFundMe account as Febe Santos, was a mother of four who had been quarantining in the basement of the home due to COVID-19, family members told Channel 2. The woman’s husband is in the hospital with the virus, the news station reported.

Firefighters battled to bring the blaze under control enough to safely enter the home through the front entrance. Four children and another woman, who Channel 2 reported was their babysitter, were able to get out with no injuries.

However, crews were stopped from moving any further when the floor became unstable, officials said.

“The flooring system had compromised,” Strother said. “It actually collapsed onto the basement, which is where we had received confirmed reports that a victim was.”

Crews were forced to halt their rescue efforts and focus on putting out the flames “to prevent significant injuries or loss of life to personnel,” the fire department said.

The victim’s body was taken to the Gwinnett County Medical Examiner’s Office for an autopsy.