HONOLULU (AP) — The National Transportation Safety Board said a team has recovered the remains of three flight crew members and the wreckage of a medical transport plane that crashed into the ocean off Maui last month.

The cockpit voice recorder, cockpit image recorder and other electronic components were retrieved from the wreckage during a deep-water search operation, the Honolulu Star-Advertiser reported Thursday.

The remnants of the twin-engine, turbine-­powered airplane will be taken to the agency's laboratory in Washington, D.C., as part of the accident investigation. The investigation is expected to take one to two years, the agency said.

Pilot Brian Treptow, flight nurse Courtney Parry and flight paramedic Gabriel Camacho were killed when the Raytheon C90A crashed shortly after leaving Kahului Airport at 8:53 p.m. on Dec. 15.

The flight was headed to Waimea on the Big Island to transport a patient to Honolulu.

The remains were being transported to Oahu on a private vessel. The Honolulu Department of the Medical Examiner said it will identify them.

The National Transportation Safety Board earlier this month said a witness saw the plane spiral down and hit the ocean.

The search area covered about 54 square miles (140 square kilometers) at depths ranging from 4,500 to 7500 feet (1,371 to 2,286 meters). The search vessel, MV Island Pride, detected a series of pings from an acoustic beacon installed on the plane’s cockpit voice recorder. Recovery crews found the wreckage at a depth of about 6,420 feet (1,957 meters).