Jennifer Homendy, chair of the National Transportation Safety Board, said the investigation into the crash was in its "early stages" and it was too soon to tell what caused it.
The Cessna Grand Caravan aircraft, operated by regional operator Bering Air, was travelling from Unalakleet to Nome on Thursday when it lost radar contact.
Nine passengers and a pilot were on board the plane when it came down in Norton Sound about 34 miles (55km) south-east of Nome, a city of about 3,500 on Alaska's west coast.
Among the dead were Rhone Baumgartner and Kameron Hartvigson, two employees of the Alaska Native Tribal Health Consortium.
They had travelled to Unalakleet to carry out maintenance work on a water plant, the non-profit organisation said on Friday.
Ms Homendy said that nine investigators are on the scene, backed up by specialists in Washington DC.
"Recovery efforts are still under way, with the priority being victim recovery," she said during a news conference in Anchorage, Alaska's largest city.
"I would like to take a moment and expend our deepest condolences to people who lost loved ones in this tragedy," she said.
Ms Homendy said recovery workers were dealing with deteriorating weather conditions and that the wreckage had landed on an ice floe which is moving at a rate of five miles a day.
In a statement, Bering Air, which operates commercial and charter flights, expressed its condolences and said it would be cooperating with the investigation into the crash.
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