Garrett Reid is behind bars. Again.

Reid, eldest son of Eagles coach Andy Reid, was sent to Graterford Prison yesterday after he failed a drug test at a Hunting Park halfway house, said Montgomery County District Attorney Risa Vetri Ferman.

The 26-year-old tested positive for narcotics when he returned to the Luzerne Treatment Center, on Luzerne Street near G, where he was serving part of a three-year probation sentence.

"He had been on a pass away from the facility for a brief period of time," Ferman said. Reports that Reid had been involved in a physical altercation at the center were unconfirmed, she added.

Reid's troubles began on Jan. 30, 2007, when his SUV rammed another car in Montgomery County, injuring the other driver. Police said Reid was high on heroin at the time.

While serving time for the car crash, Reid smuggled 89 pills into prison in his rectum. He was sentenced last summer to a drug-treatment program for nonviolent offenders. Reid served five months in state prison and was then moved to the halfway house, where he's subject to frequent drug tests, Ferman said. *