Hours after the U.S. Forest Service warned people to stay away from a popular Mendenhall Glacier ice cave, the entrance collapsed.

Guiding company co-owner Becky Janes of Above and Beyond Alaska notified the Forest Service at noon Friday of the collapsed entrance. Above and Beyond Alaska is one of two commercial guiding companies holding permits to escort visitors along the west side of Mendenhall Glacier.

While part of the cave is still freestanding and may appear intact, Forest Service officials continued their call for people to stay away.

“The ice cave remains unstable and unsafe,” said Mendenhall Glacier Visitor Center Director John Neary. “The collapse is a sign of structural weakness in the ice that may extend beyond the freshly broken ice.”