ORANGE - Three people were killed and a fourth person was injured when a fire broke out overnight in a vacant building in Orange.

Police say an on-duty police officer was patrolling the area of Reock Street when she spotted smoke coming from the building at around 1 a.m. She is being credited with saving the life of one person who was inside the buidling.

Firefighters found the bodies of three other men who were apparently trapped on the building's upper floors. The identities of the deceased have not yet been released.

Police say the men were apparently squatters who may have been using some sort of heating source or cooking device. The building had no electricity or running water, according to investigators.

Officials are urging residents to contact police if they notice homeless people living in abandoned buildings, so that similar tragedies can be avoided.

The cause of the fire remains unclear. The arson and homicide divisions of the Essex County Prosecutor's Office are investigatng.