An explosion in a building in New York’s Chinatown has injured dozens of people, including firefighters sent in to fight the blaze. Three people were in serious condition and others, including four firefighters, were less serious with burns and other injuries.

USA Today reports that an emergency call came in at about 12:45 p.m. today. Firefighters say they arrived at the front door of the building to find fire at the back. The building is five stories tall and has businesses on the ground floor and residences in the upper floors.

Firefighters said there had been an explosion on the first floor that had caused a partial collapse, but nothing structural. The cause of that explosion is currently unknown, though there have been various reports of possible causes and location centers.

Firefighters do know that there were pesticide canisters in the building, and possibly they exploded in the fire, But firemen do not know at this point what exactly happened. The fire itself was under control shortly afar 1:30 p.m.

Building residents describe hearing booming sounds, like a bomb, and feeling an impact like an earthquake. One saw firefighters carrying a woman out with an injured leg. Most of the injuries in the building were on the second and third floors, the residential areas of the building.

Some witnesses reported seeing firefighters pulling a man from an upper story using the bucket of a raised rescue tower ladder.

The New York Daily News cited a natural gas explosion as the cause, mentioning a severed gas line in the basement. There were reports that the rear of the building may have been under construction. While the New York Post reported that the explosion happened at the back of a new beauty salon under construction in the building.

Assistant Fire Chief Robert Boyce told the Post there were “existing code violations for this building and we are looking into that.”