It happened around 1 a.m. on Mohawk Street in northeast Houston.
Two firefighters went inside the house, but as the smoke and heat grew worse, the roof collapsed. That's when they indicated to their crew they were in trouble and called for help, HFD said.
Both firefighters were able to escape to safety.
Firefighters said the fire was caused by a candle the family used after their neighborhood lost power due to a storm.
"It happened really quick," said an HFD firefighter. "The homeowner said it happened in a blink of an eye, but they were able to get out."
The homeowners and their two children also escaped the fire safely. No injuries were reported.