By Kim Palmer

COLUMBUS, Ohio (Reuters) - An Ohio death row inmate was found hanged in his prison cell on Sunday, three days before he was due to be executed for the 1987 murder of a babysitter, a prison spokeswoman said.

Billy Slagle, 44, had been due to receive a lethal injection at 10 a.m. on Wednesday, according to JoEllen Smith, spokeswoman for the Ohio Department of Rehabilitation and Correction. She said an investigation into Slagle's death was ongoing.

Slagle, who spent 24 years on death row, was convicted in 1988 of the robbery and murder of Mari Anne Pope in Cleveland. Pope, 44, was watching her neighbor's two young children when Slagle broke in and stabbed her 17 times with a pair of scissors.

Slagle's body was found at the Chillicothe Correctional Institution. He was due to be transferred to the Southern Ohio Correctional Facility in Lucasville in preparation for his execution.

Ohio Governor John Kasich, a Republican, declined to commute Slagle's death sentence to life in prison last month after the state parole board voted against recommending clemency.

Cuyahoga County Prosecutor Tim McGinty recommended Slagle's death sentence be commuted at his clemency hearing. Slagle had said at the July hearing that his judgment was severely impaired by drugs and alcohol when he broke into Pope's home.

Since the death penalty was reinstated in the United States in 1976, Ohio has executed 51 inmates, according to the Death Penalty Information Center. There are more than 140 prisoners on death row in the state.

(Editing by Cynthia Johnston and Paul Simao)