Fire officials are investigating the cause of Thursday's early-morning fire in Brooklyn that injured five firefighters, two of them seriously – hours after another fire in the borough claimed the life of a man.

Flames broke out around 4:30 a.m. on the first floor of a three-story single-family home on 192 Concord Street in Downtown Brooklyn.

Residents on the block between Duffield and Gold Streets were evacuated from their buildings.

"We just walked up after being out and there were massive flames coming out of the building. It was pretty intense," said resident Josh Stoddard.

"I actually ran out of the building with just my jacket on and a pair of shoes. No socks, no money, no keys, no phone," said Gary Nebiol, the owner of a neighboring building.

The fire was brought under control around two hours later, but not before heavy smoke and fire forced the New York City Fire Department to attack the flames from the outside.

“The units made a tremendous push to get up the stairs, but there was just a tremendous volume of fire,” said FDNY Deputy Chief Vincent Mandala. “We ended up back out and using the tower ladder to put out the fire.”

Several firefighters were injured on the way out of the building.

"Two of the firefighters were injured seriously as they were exiting the building,” said Mandala. “The banister for the stairwell gave way and they both came down on top of each other. So they were transported to Bellevue immediately. And the other three were minor burns and whatnot, just usual firefighting injuries."

The Red Cross is helping people displaced by the fire, which gutted the building and forced the temporary evacuation of residents along the block.

It is not clear how the fire started but investigators say it does not appear to be suspicious.

"They're telling us that they don't know about the structural integrity of this building, so they had us pack up a few clothes and they have to inspect the building before they can let us back in,” said neighbor Lauren Bahr.

The temporary location is less than ideal, but Bahr said she understands it could have been so much worse.

“I feel very lucky that no one was hurt,” she said. “Everyone in our building is safe and sound and that's what really matters.”

The fire came hours after a deadly fire in Bushwick.

Flames broke out around 10:30 p.m. Wednesday at 732 Decatur Street.

Eddie Ortiz, 35, was killed in the blaze.

Two others, an 81-year-old man and 40-year-old woman, were hospitalized in stable condition.