GRESHAM, Ore. (AP) — The Oregon Department of Human Services faces a $1.5 million lawsuit filed on behalf of a 7-year-old boy who was placed in his father's care despite a court order banning the man from seeing his two younger sons, a newspaper reported Thursday.

Robert A. Lamb is charged with criminal mistreatment and assault, both felonies, involving the treatment of his son, The Oregonian/OregonLive reported.

A warrant was issued for Lamb's arrest after he missed a May court hearing.

The child had no relationship with his 44-year-old father before being placed with him when his mother went to jail. He lived there five months before being removed from the home. He remains in foster care

The lawsuit filed in Multnomah County Circuit Court alleges a background check should have turned up a violent past going back years, including Lamb's conviction in 2008 for choking his girlfriend and a 2016 restraining order involving his other children.

Christine Stone, a DHS spokeswoman, says a child is never placed in care before a background check is done.

State law prohibits anyone who's ever been convicted of abuse against a child or a spouse of being a caregiver. It wasn't immediately clear why the boy was placed with Lamb.

The agency is clearing a backlog of 15,000 unprocessed background checks that can take as long a month each to complete. Twenty-four workers have been hired to speed the process and six more will be added, the agency said.

Authorities were tipped off to the allegations of abuse when a school bus driver noticed the child was in obvious pain as he struggled to get on board.

The bus driver told his school, and the boy told the principal that sitting was painful because of his injuries. He said he couldn't straighten his pinky finger because his father had smashed it with a spatula, the newspaper reported.

Eventually, the boy said his father slapped his head, smacked his hands, whipped his back and legs with a belt and forced him to run in his pajamas through their snowy backyard, police records say.

He fell and each time he tried to get up, the boy said, his dad pushed him back to the ground.