SAN MATEO, California — It could take weeks to figure out why a white stretch limousine caught fire over the weekend, turning a celebratory bachelorette party deadly, authorities said Monday.

Nine passengers were traveling in the Lincoln as it headed across the San Francisco Bay along the San Mateo-Hayward Bridge on Saturday night. Only four came out alive.

The bride, 31-year-old Neriza Fojas, was among the dead.

The vehicle is listed with California’s Public Utility Commission as legally carrying eight passengers or fewer, so it was in violation, Mike Maskarich, commander of the California Highway Patrol in Redwood City, said Monday.

The driver, who escaped uninjured, had the proper license, Maskarich said.

“The flames were gigantic,” said Roxanne Guzman, who was in a car crossing the bridge at about 10 p.m. Saturday. “The flames were so big and radiating so much heat that I could feel the heat off of my face, and I was in my car the entire time.”

Maskarich said a passenger in the limo alerted the driver that there was smoke in the passenger compartment. The driver pulled over, and “the vehicle quickly became engulfed in flames,” Maskarich said.

The four passengers who got out suffered smoke inhalation and burn “injuries of varying degrees.” The others “succumbed to the smoke and flames.”

The victims were found in the car, pressed against the partition between the passenger compartment and the driver’s area, authorities said.

Fire officials said a crew responded quickly, but it was too late to save the victims.

“Looking at the photos, it appears it started in the trunk,” California Highway Patrol spokesman Ron Simmons said Sunday. “But at this time, we don’t know officially if the fire started inside the vehicle or on the exterior.”

Lovela Nicolas, the sister-in-law of Fojas’ sister, said Fojas was a registered nurse.

“Neriza was getting married, going to the Philippines to get married there and have a ceremony there and the reception,” Nicolas told CNN from her home in Honolulu.

The mother of one of the surviving women told CNN affiliate KTVU that her daughter, Mary Guardiano, was upset but physically OK.

“She’s very sad. She is crying,” said Rosita Guardiano.

In a written statement, the limousine company said it was “deeply saddened” by the deaths.

“LimoStop Inc. will do everything possible to investigate and assist authorities in determining the cause of this fire in order to help bring forth answers and provide closure to the victims and their families,” it said.

Medical examiners may need up to two days to positively identify the remains, San Mateo County Deputy Coroner Roger Fielding said.

— CNN’s Jackie Castillo, Nick Valencia, Jake Carpenter and Justin Lear contributed to this report.