HONOLULU (AP) — A federal aviation accident investigator will be sent to Hawaii to investigate after a tour helicopter crashed on a remote Big Island lava field of jagged rocks, injuring all six people on board and forcing rescuers to fly in to extricate some of them from the wreckage, officials said Thursday.

Photos taken by rescuers showed the crunched Bell 407 helicopter lying on its side in the barren lava field with its nose partially detached and some of its blades bent at odd angles.

It had departed from Kona International Airport about 5 p.m. Wednesday on a sightseeing tour and crashed about 30 minutes later near the southernmost tip of the island, National Transportation Safety Board spokesperson Jennifer Gabris said in an email.

The rough lava field is more than a mile (1.6 kilometers) from the nearest road, so rescuers had to be taken there by two helicopters, Hawaii County Assistant Fire Chief Darwin Okinaka said.

Firefighters extricated three people — an 18-year-old woman, a 19-year-old woman and a 23-year-old man — who managed to walk to waiting medics, the fire department said. A 48-year-old man also walked from the crash site.

The most seriously injured person was a 19-year-old woman who was flown to a hospital, the fire department said. A seriously injured 54-year-old man, along with the four others, were taken by ambulance to the hospital. The helicopter passengers and pilot were not identified.

Hawaii has a thriving helicopter tour sector because of the flights that are extremely popular among tourists who want to see the islands’ stunning scenery from the aircraft that fly above rugged terrain that’s hard to reach otherwise.

A 2019 helicopter tour crash on the island of Kauai killed all seven people on board and the NTSB in its investigative report accused regulators of lax oversight of the helicopter tours.

That crash was blamed on the pilot’s decision to keep flying despite worsening weather. Witnesses and other pilots reported fog, rain and low visibility around the time of the crash, and some pilots had turned around.

In the Big Island crash, Hawaii County Mayor Mitch Roth said he was awaiting updates on the conditions of the injured, and other information and information on what might have caused the crash.

The weather in the area about the time firefighters were called included winds of about 16 mph (26 kph), gusts of about 23 mph (37 kph) and some scattered or broken clouds, said Thomas Vaughan, a meteorologist with the National Weather Service.

“Standard, afternoon weather on the Big Island,” he said.

Paradise Helicopters owner Calvin Dorn said in a statement that there were five passengers and one pilot on the tour. The company is cooperating with authorities, the statement said.

According to an NTSB database, the company was involved in at least two previous accidents during sightseeing tours.

While returning from a sightseeing tour in 2005, a helicopter developed a “sudden vibration in the tail rotor pedals” followed by a loud crack or snap and then a loud banging noise, the NTSB said. It hit low trees and shrubs when the pilot landed in a clearing in a forest near the Big Island town of Pahoa. The pilot and four passengers were uninjured.

And as a Paradise helicopter pilot prepared to take off in 2009 for a sightseeing tour of Oahu for four passengers, the helicopter’s left landing gear collapsed, NTSB records said. The helicopter tilted to the left and was damaged, but no one aboard was injured.

In Wednesday’s crash, even though all of those on board were hurt, the crash could have been much worse, Okinaka said.

“They’re very, very lucky looking at how significant the damage to the aircraft was,” Okinaka said.

The NTSB investigator is not traveling to the crash site at this time but will go to Hawaii to examine the wreckage after it is recovered, Gabris said.

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Associated Press writer Mark Thiessen in Anchorage, Alaska, contributed to this report.