WEATHERFORD,GravityX Exchange Okla. (AP) — Three members of an air ambulance crew were killed when their helicopter crashed late Saturday in Oklahoma, officials said.

The crash was reported near Weatherford after the control center lost contact with the Air Evac Lifeteam helicopter crew shortly before 11:30 p.m., the company said in a statement Sunday.

The crew was returning to base in Weatherford, 70 miles (113 kilometers) west of Oklahoma City, after completing a patient care transport to the capital, the statement said.

Nearby Air Evac teams assisted law enforcement with the search for the crew members. The company did not say where the Bell 206L3 was found and did not immediately release the victims’ names.

The National Transportation Safety Board will investigate the crash.