Oklahoma authorities say they found evidence of foul play in the suspicious disappearance of two women who went missing on Saturday while picking up children.

Veronica Butler, 27, and her friend Jillian Kelley, 39, were on their way to pick up Butlers 6-year-old daughter and 8-year-old son in Eva, Oklahoma, for her daughters birthday, a source close to Butler told ABC affiliate KVII . But the women never made it to the pick up location, the Texas County Sheriffs Department said in an advisory last week.

The Oklahoma State Bureau of Investigation could not confirm the womens exact relationship or where they were going, telling the outlet that the situation was still under investigation.