WATCH: Failure with boiler causes University of Nevada, Reno dorm explosion

RENO (KTNV) — We now know what caused two explosions that damaged Argenta and Nye Halls at University of Nevada, Reno back in July.

A "catastrophic failure" within a boiler in Argenta Hall "ignited the series of events" that led to a the explosions on campus, the Nevada Department of Public Safety says.

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According to the investigation summary, a technician was repairing a boiler at the dorm on July 5 when it backfired. This caused the first explosion and detached a gas line from the boiler.

Firefighters were called to the scene.

The technician shut off the supply gas to Argenta Hall, but the report says gas from the severed pipe had already entered the basement area.

The sprinkler system had extinguished the initial fire and allowed the gas to move freely through the building and up the elevator shaft, the report says.

Natural gas filled the first floors and the elevator shaft adjacent to the boilers. This gas leak led to a second, larger explosion.

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According to the report, the source for the second explosion was never found.

Authorities say it could have been caused by cafeteria cooking equipment, dormitory laundry equipment, elevator cars operating, or something else in the dorm.

The second explosion was much bigger. Reno Fire Department upgraded the alarm response due to the magnitude of the explosion, the report says.

There were no deaths from the explosion, and authorities say it was not criminal or terror related.

Numerous federal, state and local fire and law enforcement agencies responded to the incident.

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Videos courtesy Nevada State Fire Marshal.