Investigators won't rule out alcohol as a factor in a crash that sent a woman to the hospital Sunday on Colorado Springs west side.

The accident occurred at about 7:45 p.m. at the intersection of Colorado Avenue and Walnut Street.

Police said a car rear-ended a motorcycle, injuring a woman riding the motorcycle.

Police have not identified the woman but described her as white and 40 years old. She was not wearing a helmet and suffered a serious head injury.

The driver of the vehicle was not injured.

Detectives with the Major Accident Unit are investigating. The investigation closed Walnut Avenue for about three hours.