Panamanian officials say a 13-year-old American girl who was the sole survivor of a plane crash in a mountainous part of the country is now being treated at a local hospital.

Francesca Lewis suffered a broken arm and hypothermia in Sunday's crash, which killed two other Americans and the pilot. The wreckage was located about 400 kilometers west of Panama City.

Francesca's mother, Valery Lewis, tells CNN that rescuers found the teenager on Tuesday under the wing of the downed aircraft and that her daughter appeared to be delirious. Lewis said it took rescuers three-and-a-half hours to get Francesca to a helicopter.

The plane crashed during what was supposed to be a brief flight that originated in the Secas Islands in the Pacific. The crash killed Francesca's friend, 13-year-old Talia Klein, Talia's father, California businessman Michael Klein, and the pilot, Edwin Lasso.

Rain and fog hampered the search for the plane. The cause of the crash is under investigation.

Michael Klein and the two girls were on vacation in Panama.

Klein was the chief executive officer of Pacificor, a Santa Barbara, California-based investment company that manages hedge funds. The company's Web site says he acquired the firm in 2002 and was responsible for its investment strategy and operations.

Some information for this report was provided by AP and Reuters.