Fire investigators have not been able to determine the cause of a fire at a Waikiki hotel restaurant Tuesday night.

The 9:51 p.m. fire at the Ocean House Restaurant in the Ocean Tower of the Outrigger Reef Hotel led to the evacuation of several hundred guests but no one was hurt.

Investigators looked at a number of possible causes but did not have enough information to pin down the source, said Capt. Terry Seelig, Honolulu Fire Department spokesman.

Flames entered the kitchen vent duct and ignited grease in the duct, which runs up to the roof of the 10-story hotel. It’s possible the fire began in the ducts although it may also have begun in the kitchen, Seelig said. The fire caused about $40,000 in damage, primarily to the hotel ducts

Firefighters shot water up the vent to extinguish the flames rather than shooting water down from the roof, which might have created more water damage to the hotel.

After the flames were extinguished, firefighters and hotel maintenence personnel discovered leaks in water pipes next to the duct. Seelig said it appeared the heat from the fire caused the pipes to expand and leak.