STILLWATER, Minn. (WCCO) – Police are investigating a fire that tore through a Twin Cities apartment complex, which has been ruled as arson.

A resident at the Birchwood Apartments in Stillwater, 14840 62nd St. N., said he heard a loud boom early Wednesday morning before everyone was forced to rush to safety.

The Red Cross is helping 16 families — 52 people total — with food, clothing and shelter. The fire displaced a total of 55, according to police.

The fire damaged four buildings in the apartment complex, which includes 16 separate apartments.

Neighbors say they heard what sounded like a loud explosion, then looked outside to see a large fire. The fire marshal and arson investigators are on the scene, working to determine a cause.

Police Chief John Gannaway said it’s too early to tell what might have caused the fire.

Police did detain someone early Wednesday, but after questioning them, they were released.