A baby was killed, and 6-year-old twins were left in critical condition, when a fire tore through a Bronx apartment building on Monday afternoon, according to authorities and sources.

The blaze erupted on the second floor of a building on Bainbridge Avenue between East 193rd Street and East 194th Street around 3:40 p.m., Malcolm Moore, FDNY assistant chief of special operations, said at a press conference.

Three children, including a  small baby covered in soot, were found inside a burning apartment and rushed outside by smoke-eaters. 

“I see them bring a little small baby out, he was so dark with soot all over him. I couldn’t even see, you know, his face or nothing,”  Valerie Ndogoula recalled. 

“I started crying and screaming, praying to God, hope he’d be OK,” she said. “It was heartbreaking, very heartbreaking.”

“The way he was covered up so dark with all that black stuff on him, I knew he wasn’t going to make it because he was so little.”

Ndogoula said the firefighters performed CPR on the baby before he was taken to the hospital. 

A 1-year-old boy was later pronounced dead in the hospital, and two 6-year-old twins, a girl and a boy, remain in critical condition, according to the NYPD and sources. 

Two other civilians were hospitalized along with three firefighters, who suffered minor injuries, officials said. 

Fire crews brought the flames under control by 4:40 p.m. 

“The fire rapidly extended up the stairs, through the bulkhead, the staircase at the top of the building, forcing people to the windows and other civilians to look for a ways out,”  Moore told reporters.  

He urged people to remember to always close the door behind them in the event of a fire to halt flames from rapidly spreading to other parts of the building.

“We have several of these fires lately, where the occupants of the apartment have fled the building and left the apartment door open,” Moore said. “That appears to be the case here again, because of the heavy amount of fire found in the hallway upon arrival.”

“Close the door, it is tough to do, it is hard to have to wrap your mind around doing that, but the minute you close that door, you give everyone else in the building an opportunity to flee, and you give yourself more time to flee by not letting the fire chase behind you.”

The cause of the fire remains under investigation.