Two sisters of a girl who was allegedly raped and impregnated four times by her father traveled to Oklahoma to help locate the unmarked grave of a baby from one of those pregnancies.

Investigators believe the remains of a 4-month-old girl discovered Saturday near Dustin in Hughes County is the first of four children born to the daughter, who is now 19.

Hughes County Sheriff Houston Yeager says the sisters drew a map of a rural plot of land west of Dustin, where the child was found buried in a shallow grave.

The remains of two other infants were discovered in Missouri.

A 47-year-old Harrisonville, Mo., man is charged in Missouri with second-degree murder, two counts of endangering the welfare of a child, second-degree statutory rape, two counts of incest and two counts of accessory abandonment of a corpse.