Three crew members died in a medical helicopter crash in Oklahoma late Saturday after transporting a patient, according to the company that runs the service.
The company, Air Evac Lifeteam, said on social media that the crew members lost contact with the company's control center about 11:23 p.m. local time while they were returning to their base in Weatherford, about 70 miles west of Oklahoma City.
The company said the crew members were headed to Weatherford after transporting a patient in Oklahoma City. The Federal Aviation Administration said that the helicopter, a Bell 206L-3, crashed about midnight, although where exactly was not immediately clear.
Air Evac Lifeteam said it would not, at this time, publicly identify the crew members and that it was turning over the investigation to the National Transportation Safety Board.
An NTSB investigator was expected to be at the crash scene Sunday to begin documenting and examining the aircraft, officials said.
The investigation will examine any recordings of air traffic control communications, radar data, weather reports, witness statements and a 72-hour background of the pilot to determine whether there were any issues that could have affected the pilot's ability to safely operate the flight, among other information.
"It is important to note that NTSB does not determine cause in the early part of the investigative process," the agency said in a statement. "This is considered the fact-gathering phase of the investigation."
Air Evac Lifeteam operates more than 150 helicopter air ambulance bases in 18 states, according to its website. Crews consist of a pilot, a flight nurse and a flight paramedic.
About 90 per cent of its patient transports originate from a rural area as defined by the Centers for Medicare and Medicaid Services, according to the company.