New York — Firefighters rescued a desperate woman hanging from a window 20 stories above the street as dozens of people were trapped inside a Manhattan high-rise Saturday in a massive blaze that was sparked by an e-bike battery, the New York City Fire Department said.

The smoky blaze reported at about 10:30 a.m. injured 38 people, including five firefighters, said FDNY Commissioner Laura Kavanagh. Two tenants of the building at 429 E. 52nd St. had life-threatening injuries.

Two dozen residents escaped to the roof of the smoke-filled building, between First Avenue and Sutton Place — and ended up stranded there, as firefighters battled the blaze 17 stories below, on the building’s 20th floor.

The fire broke out when a lithium-ion battery attached to an e-bike exploded by the front door of a 20th-floor apartment front door, said FDNY Chief Fire Marshall Daniel Flynn.

Two tenants unable to escape by the front door instead tried to go out a window.

Video posted to Twitter showed a woman hanging from a window ledge of the apartment as the blaze raged inside. Her left arm was wrapped in a drape, said witness Ken Gunsberger.

“(There were) massive amounts of smoke coming out of a window,” Gunsberger said. “(The tenants were) literally choking from smoke.

The women hung on for her life for five minutes, Gunsberger said. “I didn’t know how she was going to stay there,” he said. “I’m like, ‘If they don’t grab her, that’s it.’”

Firefighters lowered oxygen tanks and masks to the trapped residents, and one firefighter rappelled down the side of the building on a rope, the video shows.

The daring firefighter grabbed the woman hanging out the window around her waist, and another firefighter also hanging from the building helped lower them to colleagues by an open window of an apartment one floor below.

“In my ENTIRE life I’ve never seen anything more #HEROIC than what i witnessed from #NYC apt.,” said Patti Ryan as she tweeted out the video.

Firefighters used the lifesaving rope to pull one more tenant from the burning apartment, the FDNY said.

FDNY Fire Chief Frank Leeb said a rope rescue “is a last resort in the FDNY.”

“What you saw today was our training our teamwork and our absolute dedication from the units that operated up there with the lifesaving rope and passing them off to our exceptionally trained EMS personnel to get these patients all off scene within a few minutes,” Leeb said.

“Our firefighters, EMS and dispatch did an extraordinary job rescuing civilians, including an incredible roof rope rescue,” Kavanagh said. “I cannot emphasize enough the incredible work that they did today.”

Firefighters went door to door as they evacuated the building, while 911 dispatchers responded to numerous calls of people trapped in their apartments.

On the 20th floor near the apartment where the blaze broke out, resident Craig Geller was awakened by his parents, who were visiting from Florida. “I did not hear an alarm,” Geller said.

Firefighters “told us to shelter in place for a while and put wet towels under the door,” Geller said.

As Geller and his parents waited for help, the “smoke kept getting much more thick,” he remembered.

“It was pretty terrifying,” he said. “Then the firefighters came, and we went down the stairs — but they were wet, and my father tripped. So now he’s in the hospital.”

Fire Marshal Flynn said a tenant in the apartment where the fire erupted ran a business repairing e-bikes and scooters. Charging e-bike or micro-mobility device batteries are blamed in nearly 200 apartment fires so far this year, he said.

“We recovered at least five e-bikes from this apartment,” the Flynn said.

Firefighters responded to the building within three minutes, Flynn said — but the fire was already raging, said Flynn.

That is common with lithium-ion battery fires, Flynn said — the batteries quickly erupt into flames.

“When they do go on fire, they are so intense that all combustibles in the area will catch fire,” Flynn said.

“This is not what we have seen traditionally where fires are slow to develop. We are encountering a fully developed fire when firefighters arrive on the scene.”

Fires sparked by lithium-ion batteries are responsible for six deaths so far this year, Flynn said..

There have been twice as many e-bike and e-scooter battery fires so far this year than in all of 2021, the Fire Department says. Last year, 104 fires were sparked by lithium-ion batteries, resulting in 79 injuries and four deaths.