A 4-alarm fire seriously damaged a 12-unit apartment building on Esplanade Avenue early Saturday morning, destroying the top half of the structure and displacing 13 residents, according to Michael Williams, a spokesman for the New Orleans Fire Department.

Williams said firefighters returning from another incident saw smoke coming from a three-story building in the 1700 block of Esplanade Avenue about 5:30 a.m.

As firefighters made their way inside, he said, residents, who had been alerted by smoke alarms, were already evacuating and knocking on doors to be sure everyone was awake.

Nelle West, one of the residents, said the fire started in the rear of the building.

“One of the tenants banged on everyone’s door to get us out,” she said.

West said firefighters were fighting the blaze within minutes. She said she hadn’t even hung up the phone with a 911 operator when units had already arrived.

According to Williams, a total of 29 units and 73 firefighters responded to the blaze.

Jon Trammel, another resident, said the fire spread fast.

“It happened so quickly, within two minutes the roof was engulfed,” he said.

According to Trammel, a large “boom” sounded a few minutes later as part of the building collapsed.

Williams said in a news release that an explosion caused a wall to pull away from the structure, and the roof and third floor eventually collapsed.

One apartment’s living room, with a copy of a Van Gogh painting on the wall, could be seen through a gaping hole at midday.

According to Williams, the fire was under control by 7:14 a.m.

He said no one was injured. The cause of the fire is still under investigation, he said.

A handful of the displaced tenants lingered across the street at midday, waiting for permission to enter and gather a few vital possessions.

Many were unsure how many of their things had survived the fire.

“I can’t even guess until I get in there,” Trammel said.

The American Red Cross offered all those displaced three nights at a hotel, but several planned to stay with friends or family.