By Steve Neavling
ticklethewire.com

An enormous fire that ripped through a converted Oakland, Calif., warehouse and killed at least 36 people broke out on the first floor, trapping people on the second floor, the ATF said.

Federal investigators said they could find no evidence of fire alarms or sprinters in the building, and Oakland officials acknowledged the building had not been inspected for three decades.

ABC 7 reports that two stairwells in the building had no exits. 

Authorities are still trying to determine what caused the fire, but no evidence of arson has surfaced.

It was the deadliest fire in a structure in the U.S. in 13 years.