DES MOINES, Iowa (AP) — Police say an early morning head-on crash killed two Des Moines police officers as well as a prisoner they were transporting and the other driver.

Police say the crash happened about 12:40 a.m. Saturday on Interstate 80 just east of Des Moines.

The officers had been returning a prisoner from Council Bluffs to Des Moines when their car was struck by a vehicle driving the wrong way on the freeway.

All four people were killed.

Interstate 80 was closed in both directions while the Iowa State Patrol investigated the crash.

Police didn't release the names of those killed until relatives could be notified. A news conference is planned Saturday.