(Reuters) - A mechanical failure probably sparked the deadly limousine fire that killed a bride and four of her friends as they crossed a bridge over the San Francisco Bay early last month, local media reported on Thursday.

The Lincoln Town Car they were riding in burst into flames when air springs in the rear of the vehicle somehow ruptured, setting off a chain of events that caused the fire, ABC7 News reported.

Neriza Fojas, 31, and eight female friends in the white stretch limousine were heading to a party across the San Mateo-Hayward Bridge to celebrate her upcoming wedding.

Fojas had married Carlo Moya in Las Vegas in a civil ceremony last year, but the couple had planned a church wedding in the Philippines for June 19, according to the Associated Press.

Authorities said at the time of the accident that the five women died as they tried to escape the burning limo through a small opening between the passenger compartment and the front seat.

Four other women suffered burns or smoke inhalation but survived the fire after getting out of the car when it stopped on the bridge.

The California Highway Patrol expects to release an official investigation report on the accident within two weeks, spokesman Art Montiel said.

"We're investigating everything in regard to the fire, including any problems with the vehicle," he said.

Investigators and San Mateo County District Attorney's Office plan to determine whether negligence was involved in the limousine's maintenance, according to local media. Reuters was not immediately able to reach the district attorney's office for comment.

(Reporting by Francesca Trianni; Editing by Scott Malone and Lisa Von Ahn)