Four people have been injured after a gas explosion at a residential building in Brooklyn on Saturday morning, officials told NY1.

Rafael Rosales lives in the unit where the explosion happened. He said he woke to the loud boom and then the cries from his roommate.

"My friend told me, 'Help me, help me,' and I go in the next room and I see my friend, he's got fire all over here," Rosales said, gesturing to his right side. "And he opened too much blood in the foot."

The explosion happened around 8:20 a.m. at a two-story residential building on Bay 49th St. near Cropsey Ave. in Gravesend.

At least one of the people injured is in serious condition, officials said.

The city's The City's Office of Emergency Management said it was a fire and natural gas explosion on the top floor.

The explosion was so intense that glass from the second-story was blown across the street.

"The whole house was shaking," recalled one neighbor, who said the explosion was loud and shook her home. "The glass was moving, the chandeliers were moving, our furniture was moving. So we were a little bit scared."

The fire was under control in a matter of minutes.

National Grid crews dug up the street in front of the building to see if the gas line had any issues.

As a precaution, the agency shut off the gas to the building, as residents living there awaited word they could return.

The cause of the explosion is under investigation.