SHERIDAN, Wyo. (AP) — A small plane crash in the mountains of northern Wyoming killed a 13-year-old girl and injured three relatives, authorities said Tuesday, adding a medical service helicopter spotted the wreckage.

The crash occurred late Monday afternoon in the area of Big Mountain, an 8,200-foot (2,500-meter) peak in the Bighorn Mountains about 15 miles (24 kilometer) west of Sheridan.

The medical helicopter spotted the downed aircraft after its crew was asked to fly over the area in Bighorn National Forest. Rescue teams set up a command post at a parking lot off a nearby highway, U.S. 14, the Sheridan County Sheriff's Office said in a statement Tuesday.

It said rescuers flown to the site found the girl dead and three seriously injured relatives — an 11-year-old boy, 53-year-old woman and 54-year-old man.

The medical chopper and another helicopter from the Wyoming Army National Guard — along with an ambulance — took two survivors to a hospital Billings, Montana, and one to a hospital in Sheridan.

As of Tuesday, authorities hadn’t released the victims’ identities or information about their flight, saying the crash was still being investigated.

Federal Aviation Administration investigators were headed to the location, according to the statement.