Story highlights 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 Fores t, 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."

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