At least four people were injured Monday during a three-alarm fire in Brooklyn.

The fire broke out inside an apartment building on Jefferson Avenue after 12:30 a.m.

News 12 spoke with a man who claimed to have witnessed the fire begin.

He says he owns and lives inside of the building and witnessed an old computer inside of his home begin smoking then catch fire.  

He says he has lived inside of the home with his son and older wife since the 1980's. 

More than 100 firefighters responded to the scene.

EMS treated people at the scene, however, three of the injured were transported to the hospital.

Fire officials say the fire also spread to two adjacent buildings causing damage. The fire is believed to have started on the second floor of the building.

The fire was under control by 3 a.m.