The cause of Friday’s apartment building fire in Waikiki was an electrical failure of an extension cord located in an adjoining balcony, the Honolulu Fire Department said.

A Honolulu fire investigator classified the cause of the blaze at 455 Nohonani St. as accidental. Damage was estimated at $527,000 to the structure and its contents.

Honolulu firefighters responded to a 911 call of a fire at the apartment complex at about 4 p.m. Friday. When crews arrived, they found smoke and flames emanating from a fourth-floor unit at the four-story building, the fire department said.

Firefighters brought the fire under control just before 4:40 p.m. and extinguished it about 5 p.m.

A family cat died in the blaze.