The Honolulu Fire Department today said investigators were unable to determine the cause of a fire that destroyed an apartment in Waipahu on Monday.

Ten units responded to a two-alarm fire at 9:35 a.m. Monday. When crews arrived, they saw smoke and flames spewing out of a unit on the second floor of a two-story apartment building.

A 50-year-old man, his wife, two adult sons and a young daughter were safely evacuated and the fire was doused at 10:46 a.m.

An investigation revealed the fire started in a small plastic storage bin that was located on a shelf in the rear bedroom of the two-bedroom apartment, HFD said in a release today. Investigators could not determine a cause of the fire due to multiple ignition sources.

The fire caused an estimated $94,000 in damages, including $85,000 to the structure and $9,000 to its contents.

It is unknown if functional smoke alarms were present in the unit. The apartment manager said smoke detectors were installed in every unit, but fire crews and witnesses did not report hearing alarms at the time of the fire, HFD said.