The FDNY says the fire that tore through a Bronx barbershop Thursday night was sparked by a lithium-ion battery.

Witness video from the scene shows firefighters racing to extinguish the smoke and flames billowing from the La Roka Barber Shop on West Burnside Avenue in the Morris Heights neighborhood of the Bronx around 9:30 p.m.

“When I was crossing the street, I saw the smoke, so I ran,” Derwin Vega said.

Vega was at the grocery store across the street and saw firefighters evacuating people from the barbershop. That’s when the flames erupted.

Firefighters got the blaze under control in less than an hour. Witnesses say employees saw the fire spread from one scooter to another. Several scooters are still inside the burned-out business.

A 29-year-old man and a 39-year-old woman who were inside the shop were rushed to Jacobi Medical Center in critical condition. Witnesses say the woman worked in the back of the shop as a hair braider and struggled to get out.

“They told me she was in the deli, so I went over there. I saw her. I know her by face, and I saw her face. Her body was burnt really bad,” Vegas said.

Three others had minor injuries and were taken to BronxCare.

Many neighborhood residents say they’re hoping this tragedy will serve as a warning of the dangers of lithium-ion batteries.

“Don’t put them inside the business. Don’t put them inside apartments — that’s what the FDNY has been saying for years,” Vega said.

The fire also damaged the Chinese restaurant next door. Fire officials say they are continuing to investigate the incident.