A fire at a three-story Baldwin apartment building Thursday has left about 145 people displaced, according to fire officials.

About 150 firefighters from Baldwin and other area departments battled the blaze that closed down a section of Merrick Road, Nassau County police and fire officials said.

Nassau County police said the apartment building was "being condemned due to partial roof collapses in several places."

Three firefighters were injured in the blaze, Nassau Chief Fire Marshal Michael F. Uttaro said in a news release. One was sent to a hospital for evaluation while the other two refused treatment.

The fire did not appear suspicious and was "related to an accidental electrical malfunction," Uttaro said.

The fire caused area power outages that impacted more than 2,000 customers, according to PSEG Long Island.

The Nassau County Fire Marshal's Office said a 911 call received at 11:25 a.m. reported smoke in the large H-shaped complex, which is located across the street from St. Christopher's Church.

Uttaro said the fire had spread "rapidly across the roof" of the building, through the top-floor cockloft and void space. He added that the building was occupied at the time of the fire, but that residents had been able to safely evacuate.

Symona Boyd was asleep in her apartment when she heard knocking on her door Thursday morning. She assumed it was the electricians who she saw arrive earlier in the morning to shut off power and do work.

"My smoke detector was going off, but I just assumed it was something with the electricians," Boyd, 60, recalled. "I smelled smoke ... it wasn’t heavy, so I got up and opened the windows and then I went back to bed."

Then she said "Fireman Steve" appeared in her bedroom and woke her up, yelling at her to evacuate. He grabbed a washcloth from her bathroom, put it on her face and escorted her downstairs and outside for medical attention.

"I was in there sleeping, inhaling smoke," Boyd said. "I had to get oxygen. The lady down the road gave me water. I was really grateful."

Boyd said "Fireman Steve" told her he was not sure if her apartment was "completely gone" or just "partially gone."

"He was really nice; he saved my life," she added. "I'm grateful."

That "lady down the road" Boyd met was Kelly Wenz, who owns a home two doors away from the building. She said she saw "thick black smoke ... billowing out of the roof."

"I’ve never seen anything like it in my life," Wenz said. "I’m just here to see if people need water or help or anything ... I’m a neighbor, it’s what you’re supposed to do. Some of these people might have lost everything."

At around 3:50 p.m., a sign reading "UNSAFE STRUCTURE DO NOT ENTER" was posted on a first-story window of the apartment building. Residents could not reenter to retrieve personal belongings, including the prom dress and the graduation cap and gown one young resident was expecting to wear on Thursday evening and Friday, respectively.

"I thought maybe it was a fire drill, so I didn't get my phone, my wallet, I just came out," said resident Dennis Cook, a Vietnam veteran.

Cook was hopeful that officials would let residents back inside "so that we can get our medicines and important papers and a few things to wear," he said. But around 4:30 p.m., crews began cutting plywood to board up the building.

"That's a bad sign," said Lenia Kiki, a mass care manager with the American Red Cross, which was gearing up to order hot meals and set up cots for residents to spend the night at St. Christopher's.

She said that with the building condemned, the nonprofit has begun coordinating with Nassau County to find places in shelters for residents to stay beyond Thursday evening and has began helping folks who need medications.