Story highlights

NEW: The victim is identified as a 34-year-old woman

The spot is popular for people wanting to get away from the heat

Sheriff's office: "We've been saying since mid-May, it's extremely dangerous"

CNN  — 

One person was killed and five others injured when an ice cave collapsed Monday in a national forest in northwest Washington state.

The collapse took place at the Big Four Ice Caves in the Mount Baker-Snoqualmie National Forest, a popular spot for people wanting to get away from the heat.

“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,” said Shari Ireton with the Snohomish County Sheriff’s Office

She said the heat weakens the caves and makes the ice more prone to melting.

“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.”

The Snohomish County Sheriff’s Office identified the person who died as a 34-year-old woman. Her body is at the back of the cave, and authorities said a safe recovery of it will be difficult, given the dangerous conditions.

Two men, a woman and two girls were also injured. The injuries to the adults were “severe,” with leg and pelvic fractures, Ireton said.

Three of those hurt were treated at Harborview Medical Center, and all of them appear to have improved, according to the Seattle hospital.

One of them, a 35-year-old woman, was treated and released Monday night.

A 25-year-old man is in an intensive care unit there, having been upgraded from critical to serious condition, the hospital said Tuesday. And a 35-year-old man has been moved out of ICU after going from serious to satisfactory condition.

Monday’s death was the first at the caves since a chunk of ice crushed an 11-year-old girl in 2010.

CNN’s Amanda Watts and Greg Botelho contributed to this report.