Three crew members of a medical air transport team died Saturday when their helicopter crashed near Hydro, about 65 miles west of Oklahoma City.

At 11:23 p.m., the operations control center for Air Evac Lifeteam lost contact with the helicopter, a Bell 206L-3, which was returning to its base in Weatherford after transporting a patient to Oklahoma City, according to a social media post by Air Evac Lifeteam.

More: ‘We are losing power,’ new pilot said before fatal crash in Oklahoma City in December

Nearby Air Evac Lifeteam crews worked with local law enforcement to find the crash site.

Information about the three victims has not been released. Crews consist of a pilot, a flight nurse and a flight paramedic, according to Air Evac Lifestream’s website.

“Our primary focus is on supporting the families and our team members,” Air Evac Lifeteam officials said in the social media post. “(Critical Incident Stress Management) teams have been sent to assist our team members during this time.”

The investigation has been turned over to the National Transportation Safety Board.

Air Evac Lifeteam operates more than 150 helicopter air ambulance bases across 18 states, according to its website. Crews are on-duty daily to respond to medical emergency scenes or transport patients between medical facilities, according to the website.

About 90 percent of Air Evac Lifeteam’s patient transports originate from a rural area.

This article originally appeared on Oklahoman: Medical helicopter crash outside OKC leaves three dead Saturday night