Ilya Salkind had been staying at a home near Mexico City and his friends reported him missing earlier this week.
Arturo Torres of the Morelos state medical office said Friday that the 63-year-old Salkind didn't have identification when he was admitted Sunday at a hospital in Cuernavaca.
Morelos Attorney General Pedro Luis Benitez Velez says Salkind was hurt while in Tepoztlan, a town about 55 miles south of Mexico City. It was unclear how he was injured.
Salkind produced "Superman" in 1978 and two sequels.