The Honolulu Fire Department said investigators were unable to determine the cause of the old Waialua Sugar Mill fire on Wednesday because of the extensive amount of damage it caused.

The investigation has concluded and the official cause is “undetermined.”

The blaze caused an estimated $1,012,500 to the structure and $180,000 to its contents.

At the time the fire broke out, no one was reportedly inside the one-story warehouse, which was used as a wood mill. No injuries were reported.

HFD responded to the 3:04 p.m. fire located at 67-106 Kealohanui St., and the first unit to arrive found it half the building involved in smoke and flames. The fire was under control at 4:29 p.m. and extinguished at 5:34 p.m.