All three people aboard a medical helicopter were killed when it crashed into a densely wooded area outside Jackson, Mississippi, on Monday while returning from transporting a patient, hospital officials said.

Two of the people were crew members who worked for the University of Mississippi Medical Center and the other was a pilot, Dr. LouAnn Woodward, the center’s top administrator, said during a news conference. The helicopter was not carrying any patients at the time of the accident, she added.

It was not clear what caused the aircraft, which the Federal Aviation Administration identified as a Eurocopter EC-135, to lose control. The FAA said that it and the National Transportation Safety Board would investigate the crash, which occurred around 1:15 p.m.

Officials identified the three people who died as Cal Wesolowski, 62, a pilot from Starkville, Mississippi; Dustin Pope, 35, a base supervisor for AirCare from Philadelphia, Mississippi; and Jakob Kindt, 37, a critical care paramedic for AirCare from Tupelo, Mississippi.

— The New York Times