Intentionally deflated. From this article:
Officials at the Metropolitan Sports Facilities Commission, which operates the dome, said two triangle panels on the north end of the stadium are damaged. Officials intentionally deflated the dome.
“You deflate it so you don’t lose the entire roof,” said Bill Lester, executive director of the Metropolitan Sports Facilities Commission. “But that’s all we’re going to talk about until we get some more detail.”
With the storm dumping nearly two feet on parts of the Twin Cities, the snow was accumulating on the Metrodome roof Saturday night.
“It was an extraordinar situation involving Mother Nature that the Dome’s roof couldn’t handle,” Terwilliger said.
He said normal procedures were being followed Saturday, with workers on the roof itself using steam and hot water to melt and remove snow. Also, the heat inside the Dome was turned up and hot air was pumped into the in-between layers.
“That didn’t work,” Terwilliger said.
“Then it got dangerous for personnel up on the roof and we decided for the sake of safety to take them off,” he said.