A child was found hanged but still alive at a mobile home, with the dead bodies of three other children and an adult nearby.
Parker County Sheriff Larry Fowler said the survivor was taken to Cook Children's Medical Center in Fort Worth. There was no immediate word on the child's condition.
Fowler had no further details but said a statement would be issued later in the day.
The bodies were found early Tuesday at the Oak Hills mobile home park, about 25 miles (40 kilometers) west of Fort Worth near Weatherford.
Against the backdrop of the threat of US sanctions, Mexico has refused to buy military helicopters from Russia