The mother of an inmate at Lieber Correctional Institution said Thursday that a strict, months-long security program for prisoners set off a riot in which her son was stabbed.

Cathy Wright, 56, of Greenville said her son also was beaten by other inmates Tuesday after they stole an officer's keys and unlocked several cells in the prison's Ashley A dorm. State records showed Wright's son, Ryan Wright, 30, was hospitalized after the disturbance.

"Being on lockdown," Cathy Wright said, "it's making them angry."

S.C. Department of Corrections spokeswoman Stephanie Givens on Thursday could not confirm Wright's account of what happened at the maximum-security prison in Ridgeville that houses more than 1,500 inmates, including 50 on death row.

No information has been released about what caused the disturbance in the prison's Ashley A wing that sent three correctional officers and five inmates to the hospital.

"The incident is under investigation," Givens said Thursday, "so the reports will take some time."

The wing has been "operating on a regimented schedule for the safety and security of inmates and staff," she said. The effort gives prisoners access to hygienic and medical care, programs and some visitation, she said.

But inmates are not allowed to move as freely about the wing under such a measure.

All wings of the prison were on lockdown during the incident, Givens said, but that measure has been lifted.

One of the three injured officers was flown to Medical University Hospital after the nearly six-hour disturbance was quelled early Wednesday. All had been released by Thursday, Givens said.

The five inmates were treated for minor injuries at a local hospital before being sent back to the prison, she said.

Wright, who spoke with her son after the ordeal, said the inmates' activities had been restricted since an officer was attacked in December. They had been told, Wright said, that the measure would be lifted Tuesday.

But when the security program remained in place, Wright added, inmates assaulted an officer, took his keys and started unlocking cells. After they opened up the cell of her son, who's serving a 20-year sentence for assault with intent to kill, the prisoners beat and stabbed him three times, his mother said.

"He was laid out for hours until the officers came in and took control," Cathy Wright said. "He was just in there bleeding."

Her son's wounds were not thought to be serious, she said. He got stitches at a hospital and later returned to the prison, she said.

Officials have not said how many inmates were involved, but Givens insisted that the public never was at risk.

The Ashley A wing, which houses more than 200 inmates, has long been a source of trouble at the prison.

Two years ago, inmates rampaged through the wing for five hours, smashing windows, trashing common areas and offices, and setting off water sprinklers. Some rooms filled with 3 feet of water. They broke off metal desk legs and used them to assault two officers.

A special prison response team took back the wing and recaptured the inmates after firing tear gas into the dorm.

The Ashley A wing had been on lockdown prior to the January 2012 riot because of several violent episodes. Some inmates and their families blamed that outburst partially on prisoners' steady diet of bologna.

Afterward, a department official said periodic violence had to be expected at a prison where some of the state's worst offenders are incarcerated.

Since 2006, at least six serious assaults, including three homicides, have been reported at Lieber.

In August 2006, 19-year-old James Belli was killed when another prisoner repeatedly plunged a shank into his neck.

In 2009, a guard survived being stabbed 14 times by two notorious killers he was escorting from death row to the recreation yard.

While serving 10 years for criminal sexual conduct with a minor, Saverio Piazzola, 72, was strangled in his cell in September 2010.

The deadly violence has continued this year.

Still unsolved is the March 3 stabbing of 30-year-old Christopher DeWayne Gale of Columbia, who was serving a 35-year sentence for murder.

Reach Andrew Knapp at 937-5414 or twitter.com/offlede. Reach Natalie Caula Hauff at 937-5594 or Twitter.com/ncaula.