Investigators are trying to determine why a stretch limousine burst into flames on a San Francisco Bay bridge, trapping and killing five of the nine women inside on a girls' night out, including a newlywed bride.

The driver, Orville Brown, said at first he misunderstood what one of the passengers in the back was saying when she complained about smelling smoke.

With the music up, he initially thought the woman was asking if she could smoke. Seconds later, he said the women knocked again, this time screaming, "Smoke, smoke!" and "Pull over," Brown told the San Francisco Chronicle.

Brown says he pulled over when a passenger smelled smoke, but that the car was ablaze within 90 seconds.

He says he helped four of the surviving women escape through the partition. One of the women ran around to the passenger door on the back side of the limo, but by then it was engulfed in flames.

"When she opened that back door, I knew it wasn't a good scene," Brown said. "I figured with all that fire that they were gone, man. There were just so many flames. Within maybe 90 seconds, the car was fully engulfed."

The limo burst into flames around 10 p.m. Saturday on the westbound San Mateo-Hayward bridge, which connects San Mateo and Alameda counties about 20 miles southeast of San Francisco.

The nine women in the white 1999 Lincoln Town Car were en route to a hotel in Foster City for a bridal shower for Innarisa Fojas, a 31-year-old registered nurse.

Fojas' sister, Rosalyn Bersamin, told the San Francisco Chronicle that Fojas and her friends, after a night on the town, were heading to the hotel to join new husband. "She was a hard worker, a loving sister," a sobbing Bersamin told the Chronicle.

The couple, who were already married, planned to repeat their marriage vows in the Philippines next month, the San Jose Mercury News reported.

The women were all sitting together in an area partitoned off from the driver, 46-year-old Orville Brown.

Brown told NBC's Today that he pulled over in the middle of the bridge when one of the passengers said she smelled smoke.

"It happened so fast, within, maybe, two minutes from us stopping, maybe 90 seconds,it was engulfed in flames," says Brown, who was not injured. "We were all just in shock and scared, crying, frustrated ... I just reach out to the families, you know, wish that we could have done more."

Two of the women who survived were in critical condition on Monday.

The five women trapped inside were found dead as firefighters doused the vehicle - all huddled near the partition, apparently unable to squeeze through.

"My guess would be they were trying to get away from the fire and use that window opening as an escape route," said San Mateo County Coroner Robert Foucrault.

The San Mateo Fire Department was looking into the cause of the fire, while the coroner's office was working with the California Highway Patrol to determine if anything criminal occurred. "We don't believe there" was, Foucrault said.

The injured, all from California, are Mary Guardiano, 42, of Alameda; Nelia Arrellano, 36, of Oakland; Amalia Loyola, 48, of San Leandro; and Jasmine Desguia, 34, of San Jose.

The Associated Press reported that Desguia and Loyola were listed in critical condition, according to Joy Alexiou, a spokeswoman for Valley Medical Center. The condition of Arrellano, who was taken to another hospital, was not known.

The company that operated the limo was identified as Limo Stop, which offers service through limousines, vans and SUVS.

The company issued a statement saying it "will do everything possible to investigate and assist authorities in determining the cause of this fire in order to bring forth answers and provide closure to (the) victims and their families."

According to records from the California Public Utilities Commission, which regulates limousine companies, Limo Stop is licensed and insured.

Haya El Nasser and Doug Stanglin, USA TODAY

Contributing: Associated Press