By Elizabeth Daley

PITTSBURGH (Reuters) - A western Pennsylvania teenager accused of stabbing 21 people at his high school in April was refused admission to a Pittsburgh psychiatric hospital due to safety concerns, a judge said on Tuesday.

Alex Hribal, who was 16 at the time of the stabbings, has been held in juvenile detention since he was arrested on April 9 at Franklin Regional High School in Murrysville, Pennsylvania. He is accused of slashing students and staff with two 8-inch kitchen knives. Westmoreland County Judge Christopher Feliciani on Friday granted a defense request to transfer the teenager to a psychiatric facility, and planned to send him to Southwood Psychiatric Hospital in Pittsburgh.

Southwood subsequently said it was unable to accommodate Hribal, according to a statement issued by the judge.

"Southwood has security concerns," Feliciani said in the statement. "Counsel for defendant is investigating other options. If a facility is approved, the defendant will be transferred. The court order remains in effect," Feliciani said.

Officials at Southwood said that due to privacy laws, they were unable to provide further information about their reasons for rejecting Hribal.

Before Southwood's decision, seven or eight other mental health facilities denied admission to the teenager, said Bruce Chambers, a forensic psychologist hired by Hribal's defense team to evaluate him.

"Because of the high-profile nature of the case and some of the misconceptions of his mental illness, some places are not wanting to take him," said Chambers, who is in private practice in Cranberry, Pennsylvania.

"Now that he has a court order ordering him to treatment maybe a few of these other facilities will accept him."

(Editing by Barbara Goldberg, Mohammad Zargham and Eric Walsh)