At about 2:40 p.m., a sheriff's dispatcher received a report that a driver was heading west on Hollister Avenue, and was possibly under the influence of alcohol or drugs, said sheriff's spokeswoman Kelly Hoover.
"A concerned citizen told a 911 operator that the female driver was swerving, running off the road, and appeared to be nodding off," Hoover said.
A short time later, the driver rear-ended another vehicle at Hollister and Storke Road, Hoover said.
The driver, a 34-year-old woman, suffered moderate injuries when her air bag deployed, Hoover said, and was taken to a local hospital.
Three occupants of the vehicle that was rear-ended received minor injuries, she said.
"Alcohol may have been a contributing factor in the accident, which is under investigation," Hoover said.
The names of those involved were not available Friday evening.