By Steve Beck

WILMINGTON, Del. (CBS) –- Four people were injured when an ambulance and a minivan collided in Delaware early Tuesday morning.

The accident happened shortly after 9 a.m. at Lancaster Avenue and North Adams Street in Wilmington.

According to investigators, a St. Francis Ambulance was responding to a medical call with its lights and sirens activated. The ambulance was traveling northbound on N. Adams Street when it collided with a minivan that was traveling eastbound on Lancaster Avenue.

The ambulance and van each had two passengers inside. All four were taken to Christiana Hospital by ambulance for treatment of minor injuries.

The cause of the crash remains under investigation.