A Coast Guard HH-65 Dolphin helicopter crashed last night during a training exercise six miles off Sand Island, killing three of four crewmembers aboard.

Search efforts were continuing for the fourth crewmember.

"This is a very difficult case because rescuers are being rescued," said Rear Adm. Manson Brown, 14th Coast Guard District commander.

Honolulu Fire Department spokesman Capt. Terry Seelig said three of four people aboard the helicopter, which crashed about 8:15 p.m., were accounted for. The three reportedly were taken to The Queen's Medical Center, where they reportedly died.

Brown said witnesses aboard a passing Air Force transport aircraft and small Coast Guard boat saw the helicopter based at Barbers Point go down. The helicopter and small boat were doing "routine training," Brown said.

Coast Guard officials said the last crash of one of its rescue helicopters occurred in 1982 on Moloka'i.

The helicopter's four-member crew was conducting search-and- rescue drills with a 47-foot motor lifeboat from Station Honolulu when it went down, a news release said.

The Coast Guard was notified of the crash by the Federal Aviation Administration and launched a C-130 search plane from Air Station Barbers Point.

A crew on board an inbound Air Force C-17 to Honolulu International Airport saw the Coast Guard helicopter go down and circled the site until a rescue boat from the Honolulu Fire Department could get on scene.

The rescue involved the 47-foot motor lifeboat, the C-17, the C-130 and helicopters from the Honolulu Fire and Police Departments.