Acting Public Safety Director Frank Lopez has ordered a prison system internal affairs investigation into a violent disturbance in a Mississippi prison earlier this year that resulted in injuries to two Hawai'i inmates.

The incident at the Tallahatchie County Correctional Center began when 20 cell doors in a prison disciplinary unit abruptly opened at 2:48 a.m. on July 17, releasing about three dozen Hawai'i inmates from their cells.

The unit was reserved for particularly unruly convicts or prison gang members, and some of the inmates who emerged from their cells immediately attacked prisoner Ronnie Lonoaea in his cell, prison officials have said.

Lonoaea was hospitalized after the attack with head and other injuries, and inmate Scott Lee, 25, suffered a broken jaw in the disturbance.

Inmates used a telephone cord to tie shut the entrance to the Special Housing Incentive Program unit to keep corrections officers out, and Tallahatchie prison staff had to drop tear gas grenades from the roof to regain control of the unit about 90 minutes later.

Hawai'i Department of Public Safety officials demanded a "high level" investigation of the incident, and Lopez said prison owner Corrections Corporation of America submitted a letter to the state outlining the company's findings.

Lopez said the summary of the CCA findings suggested the doors opened because an officer accidentally pushed the wrong button.

Prison officials have said a relief sergeant pushed the button that released the inmates, and both the sergeant and the captain responsible for overseeing the unit no longer work at the prison.

CCA officials said they installed a fail-safe device to prevent staff from accidentally opening the doors all at once, and retrained prison staff in the use of the release mechanism.

Lopez said he is not questioning CCA's findings, but said he ordered the state internal affairs investigation in late October because he wanted more information on whether there might be gang involvement, and whether prison staff in any way "worked with" the inmates in the incident.

"I have further questions that they didn't answer," Lopez said.

Lopez said the Hawai'i investigators traveled to the Mississippi prison as part of the investigation, and have requested videotape of the disturbance.

Lonoaea has been released from the hospital and moved to the Florence Correctional Center in Arizona, where he is in protective custody, said Shari Kimoto, administrator of the Department of Public Safety's Mainland branch.

Windward O'ahu resident Sandra Cooper, who is Scott Lee's mother, said her son was attacked after the cell doors in the unit opened, but said prison staff accused Lee of misconduct in the incident. Cooper said she is glad to hear the state is investigating the disturbance, but skeptical the investigation will accomplish much.

"From the very beginning I have asked who pressed that button," Cooper said. "I still want them held accountable, as they're holding our children and our family accountable for everything they've done."

The state expects to pay about $36 million this year to Corrections Corporation of America to house about 1,850 Hawai'i convicts in CCA prisons in Mississippi, Oklahoma, Arizona and Kentucky because there is not enough room for them in Hawai'i prisons.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.