Updated

A suburban Atlanta couple accused of locking their son in the basement of their home for more than a year were charged with child cruelty and false imprisonment, police said Thursday.

The Buford couple is accused of confining the 13-year-old boy to a small room with a mattress and a makeshift toilet, Gwinnett County police spokesman Jake Smith said.

Authorities began investigating after the Georgia Division of Family and Children Services received an anonymous tip June 15, Smith said. The boy's parents told authorities that their son was being locked in the basement for disciplinary reasons, Smith said.

The parents were expected to surrender to authorities Friday, Smith said. A telephone message left at their house was not immediately returned.

The teen was imprisoned for much of the past two years with no access to books, toys or entertainment devices, authorities said. He was kept away from his nine siblings and did not attend school, police said.

The room was in good condition, but there was no bulb in the light fixture and the only window had been painted white — letting in a limited amount of light, authorities said. Two of the room's walls were concrete and two were made of sheet rock painted blue, investigators said. The door was fitted with a lock from the outside in January 2013, police said.

The teen didn't appear malnourished and he and his siblings showed no signs of physical abuse, police said.

The Georgia Division of Family and Children Services has custody of the boy and his siblings.