A small medical plane crashed in the Sierra Blanca mountain range in New Mexico early Thursday, killing all four people onboard, officials said.

The plane, a Beechcraft King Air 90, went down near the village of Ruidoso at about 4 a.m., the Federal Aviation Administration said on Thursday morning.

The agency said that the flight had departed from Roswell Air Center and was headed to Sierra Blanca Regional Airport, a flight of less than 30 minutes. The cause of the crash is not known, officials said.

The F.A.A. and National Transportation Safety Board will investigate, and the N.T.S.B. will be in charge of the investigation, the F.A.A. said.

This is a developing story.