Four people have been arrested on murder charges in connection with the disappearance of two mothers in rural Oklahoma, including the mother-in-law of one of the victims.

Veronica Butler, 27, and 39-year-old Jillian Kelley, a preacher's wife, disappeared while they were traveling across state lines to pick up their children. 

Their vehicle was found abandoned near Highway 95 in Texas County, and the Oklahoma State Bureau of Investigation said there was evidence to indicate foul play.

On Saturday, Tifany Machel Adams, 54, Tad Bert Cullum, 43, Cole Earl Twombly, 50, and Cora Twombly, 44, were arrested in Texas and Cimarron Counties in connection with the case, according to authorities.

Adams was Bulter's mother-in-law, according to the Daily Mail, and the children were living with her.  Cullum is Adams' boyfriend, according to the report.

All four were booked into the Texas County Jail on two counts of first-degree murder, two counts of kidnapping and one count of conspiracy to commit murder in the first degree.

Police located the bodies believed to be of the two victims on Sunday.

Court documents reviewed by the Christian Post showed that Butler, the father of her children, as well as his family were involved in a bitter custody dispute.

In a motion reportedly filed last November, Adams opposed any adjustment in the supervised visitation arrangement Butler had with the children.

She allegedly claimed that the children had been exposed to sexual abuse while under her care.

Kelley is the wife of a pastor at Hugoton First Christian Church in Kansas. Her husband, Heath Kelley, recently agreed to serve as the new pastor of Willow Christian Church in Nebraska.