Norwalk police are investigating what caused a van to catch fire and explode Saturday night.

Police and fire officials say the explosion occurred behind the All Saints Catholic School on West Rocks Road around 8 p.m. Saturday. One witness who lives across the street says the explosion felt like an earthquake.

According to another witness Sunday, two vehicles - one black, one white - fled the parking lot immediately following the explosion. A third witness claims he felt the explosion at his home, which is more than one-half mile away.

The Norwalk Police Detective Bureau and the Norwalk Fire Marshal's Office are working together on the investigation. No injuries have been reported.