An investigation into the cause of a Friday evening fire at the shuttered New Jersey Avenue School is ongoing, said Andrew Kramer, spokesman for the city.According to the Press of Atlantic City crews were called to New Jersey and Arctic avenues about 6:05 p.m. Friday for the blaze, which reached three alarms. The building was unoccupied when firefighters arrived.Preliminary reports show the fire started in the center of the building. It then spread to a large series of fires on all three floors. No injuries were reported.