The four Americans and their Kenyan pilot died when the aircraft came down in Lake Turkana, Central Island National Park on Sunday.
There were no survivors.
It is unclear what caused the accident.
"Available information indicates that two helicopters had landed earlier at Labolo tented Camp on the National Park's Island, however one managed to clear the area safely," a spokesperson for the country's National Police Service said.
Officials did not publicly identify the victims and said that next-of-kin had to be notified first.
The crash comes less than a month after three US citizens were among five who died in a plane crash in the west of the country.
Additional reporting by agencies
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