Officials say the deadly fire was sparked by the failure of the limo's rear suspension system. The driver will pay a fine for having too many passengers in the car, but won't face any other charges. NBC's Lester Holt reports.

Officials on Monday announced that the horrific limousine fire that killed five California nurses celebrating a bridal shower was “accidental in nature” and caused by a mechanical problem.

Investigators found that the lethal inferno was sparked by a “catastrophic failure” of the vehicle’s rear suspension system, said California Highway Patrol Capt. Mike Maskarich.

Authorities said that investigators found no evidence of criminal wrongdoing, adding that no criminal charges will be filed.

However, the state’s Public Utilities Commission does plan to fine the owners of the limo company $1,500 for transporting a total of nine passengers — one more than permitted per regulations, said Brigadier General Jack Hagen of the California Public Utilities Commission.

“Some tragedies are crimes and some are not. This one is not,” said San Mateo County District Attorney Steve Wagstaffe, who reviewed investigators’ findings.

The stretch limousine burst into flames while a nurse, Neriza Fojas, was celebrating her nuptials with a group of friends — all nurses, according to NBCBayArea.com. Fojas and four other women became trapped inside the vehicle and died at the scene.

The California Highway Patrol determines that the limo fire that killed five women was an accident caused by friction from the rear drive shaft coming into contact with the floor pan of the vehicle.

Autopsies and additional tests showed that the cause of death for the five women was smoke inhalation associated with a fire, San Mateo County Coroner Robert Foucrault said at Monday's news conference.

Four other passengers who escaped through the 1999 Lincoln Town Car's narrow partition dividing the front and rear ends of the limo survived the deadly blaze. The limo driver, Orville Brown, also survived.

Brown, 46, said he heard commotion in the rear of the vehicle and thought one of the nine female passengers was asking him to pull over on the shoulder of the San Mateo-Hayward Bridge so she could smoke a cigarette.

But Brown quickly realized that the woman was crying out for help — shouting "Smoke, smoke!" — as a fast-moving blaze and thick plumes of smoke engulfed the back half of the limousine.

He told investigators that he helped the four survivors escape through the partition.

In July, Brown's estranged wife, Rachel Hernandez-Brown, told NBC Bay Area that she had been arguing with him on the phone just minutes before the limo erupted in flames.

But authorities determined that a review of Brown's phone records showed that he was not using his cell when the blaze broke out, Maskarich said on Monday.