The Federal Aviation Administration and the National Transportation Safety Board are investigating a deadly plane crash in North Dakota involving an air ambulance.

The crash happened Sunday night.

The plane was on its way to Williston, North Dakota from Bismarck, North Dakota to pick up a patient when it disappeared.

Deputies found the wreckage in a remote area in Morton County on Monday.

All three people on board — the pilot, a nurse and a paramedic — were killed.

Officials are still trying to figure out what happened.