RENO, Nev. (AP) — A "catastrophic failure" in a basement boiler triggered the July 5 natural gas explosion that blew out windows and walls at a dormitory at the University of Nevada, Reno, the state fire marshal said Thursday.
The blast left eight people with minor injuries and has shut down the dorm for two years and a neighboring residence hall for at least a year.
Fire Marshal Bart Chambers said earlier that a private contractor had been working on a boiler that had been shut down days before due to mechanical problems just before the explosion on a campus mostly empty for the holiday weekend.
A summary of the investigative report released Thursday said the explosion of the boiler caused a gas leak, fire and a second, larger explosion sparked by an unknown ignition source.
"The report concludes that a catastrophic failure within boiler #1 ignited a series of events leading up to the second explosion," the report summary said. "The explosion was not criminal or terror-related."
Some 1,300 students who had been scheduled to live in the most heavily damaged dorm, Argenta Hall, and neighboring Nye Hall are being housed this school year at a downtown Reno hotel-casino tower renovated exclusively for the university and dubbed "Wolf Pack Tower."
Chambers said days after the blast that the first two floors of Argenta Hall still looked like they were hit by a major earthquake.
"Twisted studs, metal, doors blown out," he said. "It was amazing what the explosion did."
The investigative report compiled by lead investigator Joseph Rodriguez said the university first reported problems with the boiler on June 30.
It went into "safety mode" the next day and a contracted technician shut it down while he waited for a replacement part to be delivered. He returned to resume work on July 5 and was repairing the boiler when it exploded at about 12:47 p.m., causing damage throughout the basement area and severing a 3-inch natural gas line to the boiler that fueled an ensuing fire, the report said.
Reno fire crews arrived about 10 minutes later and the technician was able to shut off the city gas supply to the dorm. But approximately 6,000 cubic feet of flammable gas already had entered the basement and began to fill the first floor and elevator shafts, the report said.
A second, larger explosion followed but the report said its ignition source couldn't be determined.
"Those sources ranged from the cafeteria cooking equipment, dormitory laundry equipment ... elevator cars operating, or an unspecified tenant ignition source in Argenta Hall," it said.
University President Marc Johnson said in a statement Thursday that school officials have anxiously awaited release of the report "and can now better understand the events that led up to this unprecedented event."
"We are very fortunate and grateful that while there were minor injuries, there were no fatalities and the explosion was not criminal or terror related," he said.
Chambers said earlier the boiler in question had no history of safety violations or active inspection issues. He said it was last inspected 18 months ago in compliance with state codes mandating checks every two years.