Sept. 14, 2012 -- A South Carolina prison guard was released late last night following a tense five-hour standoff, after inmates using contraband cell phones tipped off authorities that the injured officer was being held hostage in a broom closet.

About 120 inmates in one dormitory of the Lee Correctional Institution, a maximum security prison in Bishopville, S.C., "overtook an officer" using homemade shanks and other weapons around 5 p.m. EDT, said department of corrections spokesman Clark Newsom.

The guard suffered lacerations on his face and was held hostage for five hours in a closet guarded by inmates, many of them convicted rapists and murderers.

Other inmates inside the prison alerted authorities to the guard's whereabouts by making phone calls from contraband mobile phones, which had previously been smuggled into the prison by throwing them over the perimeter fence, Newsom said.

The state department of corrections directed hostage negotiators and SWAT teams to the prison, where a standoff ensued for nearly five hours.

At 9:34 p.m. a special operations team stormed the prison and found the guard, freeing him within 15 minutes and suppressing the riot.

The guard, who officials have not identified, had "lacerations from homemade shanks but was in pretty good condition and did not seem to be injured seriously," said Newsom. Nevertheless, he was "taken to a local hospital by helicopter as a precaution."

The spokesman said the attack on the guard was a crime of "opportunity" and did not appear to have been planned.

Authorities did a search of the prison and confiscated contraband including cell phones. The prison remains on lockdown.