UPDATE 1-Helicopter crash kills four Americans and their pilot in Kenya

Four Americans and their Kenyan pilot were killed when their helicopter crashed shortly after taking off from a remote island in Lake Turkana in a national park in northwest Kenya, officials said on Monday.

The aircraft came down in Central Island National Park at around 8 p.m. on Sunday, Kenya's National Police Service said on its twitter feed, killing all on board. The cause of the crash had yet to be determined.

Kenya Civil Aviation Authority (KCAA) said two helicopters took off from the island on Sunday night heading for Lobolo Camp on the mainland. Rescuers found the wreckage early on Monday morning, Gilbert Kibe, director general of the KCAA, said in a statement. "Shortly after take-off, unfortunately one of the helicopters, a Bell 505, registration 5YKDL, lost contact and crashed on the island," Kibe said.

Police did not identify the victims, saying next of kin had to be notified first. The crash comes less than a month after three Americans were among five who died in a plane crash in the west of the country. (Reporting and writing by Hereward Holland; Editing by Robert Birsel and Toby Chopra)