Portions of a maximum-security South Carolina prison were on lockdown Thursday as officials investigated an inmate disturbance that led guards to use tear gas, then seal off and abandon a wing of the prison for more than two hours.

The disturbance at Lee Correctional Institution in Bishopville started when some inmates refused to return to their cells after dinner around 5:30 p.m. Wednesday, officials said. The two guards in the dormitory of about 150 inmates called for backup when they couldn't get the inmates to follow orders.

The guards opted to release tear gas, then seal and abandon the wing as they waited for help, prisons agency spokesman Josh Gelinas said. The inmates remained locked in the tear gas-filled unit until about 8 p.m., when members of a special operations team arrived from other prison facilities, entered the unit and placed the prisoners back in their cells.

Three inmates were treated for minor injuries; no guards were injured.

The guards that chose to flee the dormitory did so because they didn't have a reasonable, safe alternative, Gelinas said.

"Our folks are just simply outnumbered," Gelinas said. "It is too risky to enter a dorm with 150 men and try to subdue them with the numbers that we have. ... It was a melee of sorts."

The guards' actions were reasonable because they were outnumbered by the inmates, said Norman Allen, a security expert. Allen, who is chairman of the Department of Criminal Justice at Trident Technical College in Charleston, trains prison guards at the school.

There have been problems at Lee Correctional Institution on the past. In December, three inmates attacked a guard, and four other officers were injured while trying to break up the fight. In 2003, a group of prisoners armed with homemade knives took over a wing and held two guards hostage for several hours. In 1999, two inmates held two hostages for about 13 hours before releasing them unharmed.

Bishopville is in northern South Carolina, about 50 miles from Columbia.