An Italian man conducting research on an Alaska glacier was missing after he fell in a stream of meltwater and went into a 2-foot-wide vertical shaft in the ice Tuesday afternoon, officials said.

The man, who hasn’t been identified pending notification of his family, was on the Mendenhall Glacier when he fell into a stream, the Alaska Department of Public Safety said in a statement Wednesday.

“The water then pushed him into a moulin, which is a vertical shaft in a glacier where meltwater funnels down,” department spokesperson Tess Williams said in an email.

Moulins carry meltwater from the glacier surface through the structure, similar to sinkholes. The opening of the hole was around 2 feet wide and filled with running water, the Public Safety Department said.

Alaska Wildlife Troopers got the report at around 1:45 p.m. Tuesday, and the two people the man was with said they couldn’t see him after he went into the opening in the ice, the department said.

Juneau Mountain Rescue responded, but it was determined too dangerous to try to locate him, pending any further leads, the department said.

On Monday, a hiker from Arizona was found dead near the Mendenhall Glacier, but he had been hiking near the glacier and not on it, Williams said.

Thomas Casey, 69, was last seen Saturday and was reported overdue to state troopers Sunday morning. Searchers found his body at 5 p.m. Monday, and he had injuries consistent with a fall, the Public Safety Department said.

Mendenhall Glacier, around 10 miles northwest of Juneau, is part of the Juneau Ice Field. The ice field covers 1,500 square miles and dates to the last ice age, according to the U.S. Forest Service.