An ice cave that is part of the Big Four Ice Caves at Mount Baker-Snoqualmie National Forest east of Seattle partially collapsed, killing a 34-year-old woman.

Eight people were in the back of the cave when the collapse took place around 5 p.m. Tuesday.  The caves had large warning signs about instability but the caves were not blocked.

“It’s not illegal to go in the caves. However, we’ve been saying since mid-May, it’s extremely dangerous with all this hot weather,” Shari Ireton with the Snohomish County Sheriff’s Office told CNN before noting that hot weather weakens the caves.

“There was a large pile of ice and rock that came down,” she said. “So it wasn’t just one big slab. … It wasn’t a piece of a shelf coming off.”

“They’re essentially a frozen-over avalanche chute sitting over a waterfall, sitting below a giant rock shoot,” Ireton added. “It’s incredibly dangerous.”

A witness told ABC that she heard a pop before the ice gave way.

“Everybody was happy. It was really cool. … [Then] we heard a pop and I got really nervous and I just look up and there’s, I see there’s this sheet of ice coming down,” said Chloe Jakubowski, 18. “I crouched down as quickly as I could and I put my hands over my head.”

“It was really scary,” she said. “I just didn’t know if those were going to be my last few moments.”

A 25-year-old man hurt in the collapse remains in intensive care at Harborview Medical Center although his status was upgraded from critical to serious.