A Bell 407 helicopter on a sightseeing tour around Hawaii island experienced a “violent upset” before it spun uncontrollably and crashed into a remote lava field June 8, causing injuries to the pilot and five passengers, the National Transportation Safety Board said in a preliminary report.

The independent federal agency released the report Wednesday that reveals details of the events moments before the crash.

The tour helicopter, with tail number N402SH and operated by K&S Helicopters, doing business as Paradise Helicopters, crashed into a lava field between the Ranchos subdivision and South Point Road at about 5:25 p.m. June 8.

According to the report, the flight departed Ellison Onizuka Kona International Airport at 5:01 p.m. for a sightseeing tour around the island.

About 30 minutes later, the helicopter “experienced a violent upset,” followed by an uncontrolled spin.

As the helicopter continued to spin, one of the passengers saw something fall off the helicopter. Investigators said she was not able to identify a specific part.

The helicopter crashed into the lava field where the pilot and two passengers suffered serious injuries and three passengers sustained minor injuries. One of the passengers called 911 to report the crash.

NTSB investigators had visited the crash site where they observed the tail boom more than 750 feet from the main wreckage that consisted of the fuselage, engine and main rotor system. The agency noted the tail boom separated from the fuselage at the tail boom attach point.

The wreckage has since been moved to a hangar on Hawaii island.

“We’re very much in the formative stages of the investigation,” said Clint Johnson, chief of the NTSB Alaska Regional Office.

Investigators have recovered key components from the wreckage that include attachment fittings which are currently being examined at a laboratory in Washington, D.C.

In a statement Wednesday, chairman Calvin Dorn of Paradise Helicopters said, “K&S Helicopters is working closely with the pilot, NTSB, FAA, and Bell, to support a thorough investigation of the June 8 accident on the Island of Hawaii.

“All Bell 407 aircraft operated by K&S Helicopters have been voluntarily grounded out of an abundance of caution until further safety determinations can be made. The company is in the process of reviewing the preliminary NTSB findings, and we will continue to work with investigators as they complete a final report.”

A final report on the probable cause of the crash is expected to be completed in 12 months or so.

Paradise Helicopters conducts sightseeing tours on Hawaii island, Oahu and Lanai.