Eight passengers were killed, along with the Guatemalan pilot and co-pilot, Civil Aviation official Jose Carlos said.
He said five of the passengers killed were Americans, but nationalities of the other three had not been determined.
Four other Americans on board were injured and were being airlifted to a hospital in the capital. Carlos did not know the hometowns of the Americans.
Aero Ruta Maya, the airline operating the plane, said only 12 people were on the plane, including the pilots, a discrepancy that could not immediately be resolved.
Joanne de Bickford, who said she was the daughter of the airline's owner and was helping manage the crisis, confirmed there were Americans on board. She said the airline did not know how many people died.
The army provided a list of passengers, but the names appeared to be garbled. The U.S. Embassy did not immediately return calls seeking comment.