Four dead in Alaska helicopter crash during research mission

A helicopter carrying three scientists and a pilot crashed in a remote region of Alaska during a research mission.
The bodies of the victims were recovered days later from the submerged wreckage in a shallow lake.
The scientists worked for the Alaska Department of Natural Resources to study the region's geology and permafrost.
The crash is under investigation by the National Transportation Safety Board.
Recovery efforts are challenged by the helicopter's remote location, requiring another aircraft to access the site.