The U.S. Navy said Tuesday four people have died in the crash of a contractor’s helicopter on the Hawaii island of Kauai.
The Pacific Missile Range Facility said the aircraft crashed on the north side of the installation shortly after 10 a.m.
The helicopter was flying in support of a training operation, it said.
The National Transportation Safety Board said in a tweet the agency is investigating the crash of the Sikorsky S-61N helicopter.
The Sikorsky S-61N is among helicopters built between 1959 and 1980 by Sikorsky Aircraft, which is now part of Lockheed Martin. It was designed to carry a substantial freight or passenger payload. One version was built to carry up to 30 passengers, according to the Igor I. Sikorsky Historical Archives website.
The helicopters were optimized for use over water, for example to support oil rig operations. Versions were also used by all branches of the U.S. military. Licensees in the United Kingdom and other countries have also built the aircraft.
A Kauai County spokesperson said county police and firefighters responded and were assisting the military. Kauai police were helping the Navy with perimeter security and investigation support, said Coco Zickos, a county spokesperson.
An investigation will be conducted to determine the cause of the accident, the range facility release said.
The Pacific Missile Range Facility is a Navy base on the western edge of Kauai where the military tests missile defense technology and various units conduct exercises.