The Honolulu Fire Department said a Wednesday night house fire at 99-129 Pooholua Drive in Aiea was accidentally caused by unattended cooking.

A pet dog was seriously injured in the fire, HFD said this afternoon.

The damage caused an estimated $720,000 to the structure, and $80,000 to its contents.

HFD said the fire broke out just before 8 p.m., displacing three residents, who were not home at the time of the blaze. Firefighters were on the scene at 8:02 p.m., after receiving a 911 call at 7:56 p.m. to the the single-family residence. The fire was extinguished at 9:05 p.m.

HFD made two searches to confirm no occupants were in the structure.

Honolulu police, meanwhile, opened a second-degree arson investigation this morning into a separate Aiea house fire from Tuesday.

According to a police report today, an unknown suspect started the fire, which was initially classified as first-degree arson.

No one had been arrested as of this morning.