PHOENIX -- Phoenix police are investigating a serious collision that sent two people to the hospital with serious injuries.

The incident happened near Central Avenue and Watkins Road before 9 a.m. Sunday.

Witnesses told police it appeared two cars were racing on Central Avenue.

One of the cars hit a tree.

Two people inside the car were taken to the hospital with serious injuries.

The second car remained on scene.

Police are investigating whether impairment was a factor.