REDWOOD CITY — Almost five weeks after five nurses were killed while trapped inside a burning limousine, the California Highway Patrol said officers have not yet finished their investigation to determine the cause of the fire.

CHP spokesman Arturo Montiel said investigators are interviewing the four surviving nurses, who with their friends had planned a night of celebration the nuptials of one of the victims, Neriza Fojas.

They have also interviewed driver Orville Brown, who has said he helped survivors escape through a partition blocking the passenger area.

Video and photos taken by witnesses are also being reviewed, and people who saw the inferno are providing details.

"Everyone is asking why it's taking so long," said Montiel. "The answer is that there were five victims here, and we want to make sure we do a thorough investigation."

Montiel said the Foster City Fire Department is responsible for determining the cause of the fire, while CHP investigators are giving the limo a mechanical inspection.

The charred remains of the vehicle are being held at Action Towing and Recovery in Redwood City.