By MATT VOLZ, Associated Press

HELENA, Mont. (AP) — Former NFL QB Ryan Leaf has been moved from a drug treatment center to the Montana State Prison for threatening a staff member and other unspecified behavioral problems at the center, a corrections official said Thursday.

The former San Diego Chargers and Washington State Cougars quarterback was charged last spring with breaking into two houses and stealing prescription painkillers near his hometown of Great Falls. He pleaded guilty in May to reduced charges, and his five-year sentence called for spending nine months in a locked drug treatment facility as an alternative to prison.

Leaf said then that he was looking forward to the treatment at Nexus Treatment Center in Lewistown. But on Thursday, the Montana Department of Corrections released a statement by Great Falls regional probation and parole administrator Dawn Handa that said Leaf will now serve his sentence in the Deer Lodge prison.

"The Montana Department of Corrections terminated Leaf from the treatment program and placed him in prison after he was found guilty of behavior that violated conditions of his drug treatment program. The violations included threatening a program staff member," Handa said in the statement.

Corrections officials did not immediately respond to a request for details of the violations or the threats.

Leaf's attorney, Kenneth Olson, did not immediately return a call for comment.

It was unclear when the threats or other behavior issues occurred. The Department of Corrections' website listing offenders says Leaf has been an inmate since Jan. 10.

The Great Falls Tribune first reported Leaf's imprisonment Thursday.

James Farren, the district attorney in the Texas county where Leaf was given probation in a plea agreement for drug charges in 2010, said his office will move to bring Leaf back to Randall County, where he could stand trial.