The Honolulu Fire Department is investigating a fire that damaged a warehouse in Waianae early Monday.

Shortly before 2:20 a.m. nine units with firefighters responded to the fire on the 87-800 block of Apana Road. The blaze was brought under control at 2:51 a.m. and extinguished at 4:07 a.m.

Emergency Medical Services said two people — a 54-year-old man and 55-year-old woman who reportedly live next to the structure — were treated at the scene for smoke inhalation. Both were in stable condition and refused transport to a hospital.

HFD spokesman Capt. Scot Seguirant said the cause of the fire is under investigation.