Jared Remy, the son of Red Sox broadcaster Jerry Remy, allegedly attacked a fellow inmate with a chair and bar of soap during an incident last week that has prompted new charges against him, a law enforcement official said.

The official, who spoke on the condition of anonymity because he was not authorized to discuss the matter, had no other details on the alleged assault, including the extent of the other inmate’s injuries.

On Friday, the Middlesex sheriff’s office confirmed that Remy, 35, allegedly attacked another inmate the day before at the Cambridge jail where Remy is awaiting trial on charges of murdering his girlfriend, Jennifer Martel, on Aug. 15 of last year.

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However, the sheriff’s office did not specify the type of weapon used in the alleged jailhouse assault.

Remy is scheduled to be arraigned April 24 in Cambridge District Court on nine assault charges stemming from the incident.

His lawyer, Edward P. Ryan Jr., said he will enter a plea of not guilty on Remy’s behalf.

“Under the best of circumstances, jail is a very difficult place,” Ryan said. “And there is a constellation of circumstances that may be at the bottom of this incident. And I expect to investigate the matter fully and prepare an appropriate defense.”

Remy is accused of fatally stabbing Martel, the mother of their 5-year-old daughter, in the Waltham apartment they shared. The child was home at the time of the alleged attack and at least one neighbor witnessed it. Remy’s socks were blood-stained when he surrendered to police.

Ryan on Monday declined to discuss defense strategies in the murder trial, which is scheduled for October.

“We’re still exploring a range of defenses in the murder case,” he said.