Big Four Ice Caves
The Big Four Ice Caves, seen in 2007.Flickr/Erica Cooper

One person died and five others were injured after tons of rock and ice collapsed near the mouth of an ice cave in Washington state on 6 July.

Two people were seriously injured in the accident, which occurred at the popular recreation spot near Seattle.

Rescue efforts were delayed for nearly 45 minutes due to a lack of mobile phone reception, the local sheriff's office said.

The body of the victim, who has not yet been identified, remained under the debris at the Big Four Ice Caves on 7 July. Five people were taken to local hospitals.

According to authorities, the body of the deceased hiker could not be recovered due to the danger posed by the melting ice.

"As soon as [the collapse] stopped I looked up and looked around me and it was extremely gruesome, honestly," hiker Chloe Jakubowski, 18, told the Seattle Times.

"Everybody there, we grabbed everybody out and helped as best we could," she said.

The caves were closed to the public following the tragedy, but warnings about the potential risk of collapse have been posted near the site over the last few weeks.

The structure of the caves has been weakened due to the recent heat wave, sheriff's spokeswoman Shari Ireton told the Times.

"They are essentially a frozen-over avalanche chute sitting over a waterfall sitting below a giant rock chute. It's incredibly dangerous," she said.

"There was a large pile of ice and rock that came down," she told the paper. "In many ways, it was similar to an avalanche."

On 5 July, a hiker filmed a section of the ice collapsing while hikers were inside, though no injuries were reported.