SAN FRANCISCO -- A lesbian was kidnapped and gang-raped by four men before being left naked on the street after they stole her car, police in California have confirmed.

A $10,000 reward has been offered for information leading to the arrest of men involved in the incident, which occurred in the San Francisco Bay Area suburb of Richmond on December 13.

Police said the 28-year-old woman was sexually assaulted after getting out of her car before the four men forced her back into her vehicle.

She was driven to a separate location where she was gang-raped for almost an hour before the men stole her car, which was recovered abandoned the following day.

Police said the incident is being investigated as a hate crime because of comments made by the attackers regarding the woman's sexual orientation. The victim's car had a rainbow sticker on its bumper, a symbol of gay pride.

"The emotional impact has changed her life," Richmond Police Department lieutenant Mark Gagan told the San Francisco Chronicle.

"It is an absolute nightmare for her to have gone through. For 45 minutes, four strangers brutalized her."

Police have described three of the woman's attackers as Latino while a fourth was African-American. The attackers are being sought on charges of robbery, kidnapping, carjacking and sexual assault.