Three tourists and the pilot died when their tour helicopter slammed into Kilauea Volcano. The pilot had sent a mayday distress call at 9:48 a.m. A few moments later, another helicopter pilot in the area spotted the downed tour helicopter.

Autopsies were scheduled today in Hilo for each of the victims, whose names were not being released until relatives could be notified.

A National Transportation Safety Board investigator flew to the Big Island today, along with two representatives from the Federal Aviation Administration, said Tweet Coleman, FAA Pacific representative.

The tour helicopter, a Hughes 500 owned and operated by Tropical Helicopters, crashed onto the site of a recent lava flow. The helicopter burst into flames upon impact.

The Tropical helicopter was 31 minutes into a 50-minute volcano tour from Hilo International Airport when the pilot radioed that he was having engine trouble, Coleman said.

Two minutes later, the copter was down. A helicopter fighting a forest fire at Hawai'i Volcanoes National Park flew over the crash site and saw the aircraft in flames, said Jim Gale, Volcanoes National Park spokesman.

The firefighting helicopter dumped water on the flames. There were no witnesses to the crash, Gale said.

"They were in the air at the same time and responded quickly and were able to get a bucket of water to put out the fire at the crash," Gale said.

This was the first fatal tour helicopter crash in the state in three years. Seven people died in July 2000 when a Blue Hawaiian Helicopters aircraft crashed into the side of 'Iao Valley on Maui.

The Hughes 500 helicopter went down about two miles inland from the Pu'u O'o vent, Coleman said.

"The helicopter was following the shoreline, flying south, and was already coming up north back to Hilo," Coleman said. "The pilot knew he had a problem and called in a mayday and that signified a major problem. A couple minutes later and the wreckage was sighted."

Coleman would not say much about the pilot's flying background but said he was experienced.

"He was familiar with the area," she said. "He was not a new pilot. He had worked for another tour company before this."

Tropical Helicopters is the same firm that had a helicopter crash-land with five people aboard in a Kea'au field on the Big Island in September 2001.

The pilot of that helicopter reported engine trouble, but no one was seriously injured in the crash that destroyed the Bell 206 helicopter in a field near the Mauna Loa Macadamia Nut farm. The pilot was credited with quick thinking for getting the passengers out of the burning aircraft.

Tropical Helicopters is registered to do business in Hawai'i as K & S Helicopters Inc. The company was incorporated in 1997 and has its headquarters in Kailua, Kona. Calvin Dorn is listed on state business registration documents as the president.

The Hughes 500 was certified by the FAA in 1999 and is a popular model worldwide, Coleman said.

The crash site, which is past the Chain of Craters Road, can only be reached by helicopter, she said.