Fire investigators have estimated the damage to the Cheesecake Factory restaurant and neighboring businesses from an early morning fire Friday at $2.5 million.

Forty firefighters from eight companies responded to the 3:32 a.m. alarm at the Royal Hawaiian Center in the heart of the tourist district.

A cleaning crew was at work when the blaze broke out in the kitchen area, said Capt. Terry Seelig, Hono­lulu Fire Department spokes­man.

The crew was evacuated and no one was injured. The two-alarm fire was under control by 4:45 a.m. and extinguished by 5:30 a.m., Seelig said.

Kalakaua Avenue was closed for 31⁄2 hours until firetrucks cleared the scene.

Seelig said the cause of the fire was a gas leak to the fryer in the kitchen that was ignited by the pilot light.

Arriving fire companies found heavy smoke in the kitchen and dining areas. The fire was confined to the kitchen, but it spread to the exhaust ducts, igniting grease in the ducts, Seelig said.

Smoke and flames could be seen coming from the roof of the restaurant, fed by the establishment’s ducts.

It was not immediately known when the restaurant, one of the busiest in Waikiki, will reopen.