RENO, Nev. -- A small explosion in a basement boiler at a University of Nevada, Reno dormitory triggered a much larger natural gas blast last week that left part of the building looking like an earthquake had struck but caused only minor injuries to eight people, officials said Tuesday.
The initial explosion occurred Friday at Argenta Hall while a contractor was working on the boiler that had developed mechanical problems and was shut down earlier in the week, state Fire Marshal Bart Chambers said.
Preliminary information showed the initial blast started a small fire that was extinguished by sprinkler systems.
Chambers said natural gas started leaking from a 3-inch-diameter feeder line to the boiler, but investigators have not yet determined how the gas ignited.
The boiler in question had no history of safety violations or active inspection issues, he said, noting it was last inspected 18 months ago in compliance with state codes mandating checks every two years.
Shannon Ellis, UNR vice president of student services, said students, faculty and staff members were "feeling incredibly grateful that there were no serious injuries and no lives were lost."
Argenta will remain closed for at least a year, possibly two. Nye Hall, a neighboring dorm damaged by the explosion, will stay closed into the fall, Ellis said.
About 200 students have been displaced and school officials were trying to establish living arrangements for 1,300 students expected for the fall semester.
One possibility would be housing some at nearby hotel-casinos, Ellis said.
Chambers said he has directed his staff to develop a plan to ensure the safety of all boiler systems at UNR and UNLV in Las Vegas, but it appears the Argenta explosion was an isolated incident. He also said no one intentionally caused the blast.
"I can safely say there was no criminal intent, at this time," Chambers said.
University officials said fewer people than normal were on campus due to the long holiday weekend.
Seven-story Argenta Hall typically houses about 750 students. Hundreds more from neighboring dorms routinely eat in the first-floor cafeteria at Argenta that suffered some of the most severe damage.
"We can't imagine almost a better scenario for such a horrible event to have happened on the July 5th of a holiday weekend when relatively few people were on campus," UNR Executive Vice President Kevin Carman said Tuesday.
Furthermore, he said, the first fire crew on scene had returned to their truck for more equipment to test for gas leaks when the second, bigger explosion occurred.
Carman said structural engineers have concluded that damage to the building was "essentially ... all superficial."
"It seems hard to believe when you look at it," he said. "They said the buildings are in great shape and we can restore them and will restore them."
Chambers said the first two floors of the dorm looked like they were hit by a major earthquake.
"Twisted studs, metal, doors blown out," he said. "It was amazing what the explosion did."