A judge has ruled that the children of missing Utah mother Susan Powell must remain in the custody of her parents.

The judge also says she won't consider returning the two boys to their father, Josh Powell, until he undergoes a psycho-sexual evaluation.

The children have been living with her parents since Josh Powell's father Steven was arrested on child porn and voyeurism charges last fall.

On Wednesday, Pierce County Superior Court Judge Kathryn Nelson agreed to the evaluation as a safety precaution.

Nelson had noted the "extreme child porn" found in the Puyallup, Wash., home where Josh was living with the two boys and his father. Josh Powell's lawyer argued that no questionable images had been proven to belong to his client.

Susan Powell vanished in December 2009. Josh Powell has been named a person of interest but denies involvement in her disappearance.