ELIZABETH CITY, N.C. -- Officials have identified two North Carolina prison employees who were killed when inmates at a sewing plant started a fire in an unsuccessful escape attempt Thursday.

They didn't disclose how officer Justin Smith and Correction Enterprises manager Veronica Darden were killed at the Pasquotank Correctional Institution in Elizabeth City. Several other employees were hurt.

In a statement, the North Carolina Department of Public Safety said: "Correctional Officer Justin Smith, 35, provided security in the Correction Enterprises Specialty Sewing Plant. He had worked as a correctional officer since 2012. Correction Enterprises Manager Veronica Darden, 50, supervised inmates working in the Specialty Sewing Plant. She had been a Correction Enterprises employee since 2007 and previously worked as a correctional officer."

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Three other prison employees remain hospitalized in critical condition at Sentara Norfolk General Hospital, the North Carolina Department of Public Safety said in a statement late Thursday, adding that seven prison employees were treated and released from Sentara Albemarle Medical Center in Elizabeth City, and four inmates were treated for injuries.

Police respond to the Pasquotank Correctional Institution in Elizabeth City, N.C. after a report of an attempted escape Oct. 12, 2017 WTKR

The inmates started the fire around 3 p.m. at a Correction Enterprises sewing plant inside prison walls, prison spokesman Keith Acree said in a statement earlier Thursday.

Darden trained about 30 inmates there to make safety vests and other embroidered items, according to officials.

After the fire was set, several inmates unsuccessfully attempted to escape, reports CBS affiliate WTKR. It wasn't clear how many inmates were involved in the escape attempt.

In an update shortly before 5:30 p.m., the North Carolina Department of Public Safety said in a tweet the facility was under lockdown and the situation had been brought under control.

Prison workers did several counts after the fire and all 725 inmates were accounted for, Acree said.

Members of the Prison Emergency Response Team responded to PCI from other state prison facilities and are assisting the local prison staff, WTKR reported. The Pasquotank County Sheriff's Department, along with the State Bureau of Investigation, are investigating the incident.

The prison near the northeast North Carolina coast can house nearly 900 adult, male felons in both high-security and minimum-custody buildings. Minimum-security prisoners work outside the walls on road gangs for the county recycling department and perform other community labor.

The public school district locked doors at three nearby schools after getting word about 3:30 p.m. of the escape attempt. The notice came as students at one of the facilities, Pasquotank High School, were just to be released for the day and after dismissal times for the elementary and middle schools, said Tammy Sawyer, a spokeswoman for Elizabeth City-Pasquotank Public Schools. Buses were ordered back to their schools with any students still in transit.

"We didn't want kids home alone or in transport with the potential situation that was unfolding," Sawyer said. Local emergency management officials said about 5 p.m. it was again safe for students to return home.

The prison has reported other incidents this year. In April, an argument between two inmates at the prison led to one prisoner stabbing the other several times in the upper torso. Two months earlier, a guard was charged with trying to smuggle illegal drugs, phones and cigarettes behind prison walls.

Gov. Roy Cooper offered his condolences for the deaths in a statement late Thursday.

"Those who work in our prisons do a difficult and demanding job that is critical to our safety," he said.