BOULDER, Colo. (KDVR) — The investigation into the cause of a fire that destroyed 81 units in a Pearl Street apartment complex was ruled undetermined by Boulder Fire-Rescue.

Investigators said the fire ignited on the outside of the building near the west side of the complex and spread quickly as the buildings were made of wood and other flammable materials. The sprinkler system both in the individual buildings and garage worked properly when they were initiated. The investigation determined there were no building code or fire violations that would have led to the blaze.

The BFR team utilized K-9 accelerant detection dogs and other techniques in the investigation and found no evidence of the fire being intentionally set.

The fire at the Whittier Place Condominiums was first reported at 3:32 a.m. on Oct. 19, 2021. It tore through several buildings in a very short time but crews got it under control within hours. There were no deaths from the fire, which was surprising considering the size and velocity of the blaze.

“This was a tremendously challenging and consuming fire. I am surprised and relieved to be able to say that it appears we had no deaths,” Fire-Rescue Chief Michael Calderazzo said the day after the fire.

The Boulder Police Department’s investigation into the fire continues as the BFR’s purpose was to determine the origin and cause of the fire.