City fire investigators were busy trying to determine the cause of two separate fires Wednesday morning in Hawaii Kai and Nanakuli.

No one was injured in both instances. Both structures were vacant.

The first alarm was turned in at 10:39 a.m. in Hawaii Kai. It took firefighters 16 minutes to bring the blaze on Kaumakani Street under control.

The fire was believed to have been started in the kitchen of the three-bedroom house. Damage was estimated at $20,000.

Damage was estimated at $10,000 in the second fire in a portable building on Farrington Highway used as a storage facility.

The Nanakuli fire was reported at 10:55 a.m. and brought under control 10 minutes later.

The damage was limited to the interior of the 15-by-15-foot storage building.