A fire that started in a New York City e-bike shop early Tuesday spread to upper-floor apartments, killing four people and injuring several others, authorities said.

City fire officials said the blaze was reported shortly after midnight on the Lower East Side of Manhattan in a six-story building that houses HQ E-Bike Repair. A pile of burned bikes, scooters and other debris was seen on the sidewalk outside the building.

Two men and two women died and two other women were hospitalized in critical condition, officials said. A firefighter suffered minor injuries, authorities said.

“We arrived in just about four minutes,” said John Sarrocco, a deputy assistant fire chief. “We found heavy fire in an e-bike store located on the first floor.”

The cause of the fire was under investigation.

A man who said he was the owner of the bike shop told The Associated Press he made his usual checks of the store before he left Monday night. He denied any e-bike batteries, which have been blamed for a series of fires across the city, were being charged.

“The shop has been there for six years, I check before I leave every night," said the man, who spoke in Mandarin in a phone interview and only gave his last name, Liu. “I checked last night, turned off the power besides the ones for the monitor and automatic door.”

He added: “I got a call from a neighbor ... and told me about the fire. I went to my shop but couldn’t get close when they were working on the fire, I saw a lot of smoke. My shop is gone, I’ve been working for nothing for years.”

Liu said he was at the police station waiting to talk with officers Tuesday morning.

The blaze startled the neighborhood in the middle of the night.

“A friend of mine came in and yelled ’there’s a fire next door,’” Belal Alayah, a neighborhood resident, told WABC-TV. “I step out. I see the flames so hot it’s going through the metal gate. I knew it was the bike store, so I called the fire department. But the fire kept getting bigger and bigger and it took them a while to stop the fire.”

Electric bikes have become popular, non-gasoline-burning ways to make deliveries, commute and zip around a city that has promoted cycling in recent decades. Many run on lithium ion batteries, which have been blamed for numerous fires.

In April in the Queens section of New York City, two children were killed in a fire blamed on an electric bicycle. Another Manhattan fire in November that injured over three dozen people was caused by a malfunctioning e-bike battery, officials said.

Last year in the city, nearly 200 fires and six deaths were tied to such batteries, with an 8-year-old girl and a 5-year-old girl among those who died in blazes linked to scooter batteries. Fire officials have repeatedly issued warnings and safety tips.

Lithium ion batteries can catch fire because they contain a flammable electrolyte solution that allows electrical current to flow, experts say. Many fires have been linked to such batteries in laptops, cellphones and other items.