Dozens of inmates were taken to area hospitals after a gas leak at York County Prison late Wednesday night.

Emergency crews were dispatched to the 3400 Concord Road prison in Springettsbury Township about 11:15 p.m. for a report of a gas leak with multiple patients.

The leak, involving carbon monoxide, or CO for short, was contained an area of the prison that holds female inmates, said Warden Mary Sabol.

All told, 49 inmates were taken to Memorial and York hospitals. Six were admitted for treatment, the warden said.

"We utilized both hospitals," she said.

Additionally, two staff members were also taken to area hospitals.

As of Thursday afternoon, all inmates who required treatment were returned to the prison, Carl Lindquist, York County spokesman, said in a news release.

Leak: Crews from as far away as Dover, Wrightsville and West Manchester Township were dispatched to the scene. Police services assisted in securing the area and provided prisoner security.

Emergency responders checked all housing units in the prison complex for carbon monoxide and also assisted in ventilating affected areas.

Prison staff became aware of the carbon monoxide leak after inmates complained of "symptoms consistent with carbon monoxide exposure," the release said.

The leak has been blamed on the heating, venting and air conditioning system that provides service to the affected area of the prison, Sabol said.

The system has been taken off line.

Investigating: Officials are investigating what caused the leak, Sabol said, adding that a company will be at the prison Friday morning to go over the system.

The housing unit primarily affected by the leak remains empty pending further investigation, the release says.

Prisoners living in the unit have been moved to other areas in the facility.

Carbon monoxide is an odorless, colorless gas that can cause sudden illness and death, according to the federal Centers for Disease Control and Prevention.

The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.

Security: The influx of patients at Memorial Hospital prompted hospital officials to call in additional medical staff to provide care, said Josette Myers, hospital spokeswoman.

Similar scenarios in which mass casualties are brought to the hospital have been practiced, and Myers said response to the gas leak incident went according to plan.

"Our staff responded really well," she said.

Because nearly all of the patients were prison inmates, Myers said, security had to be stepped up.

Hospital officials increased onsite security, and the prison provided correctional officers.

"They had a guard (correctional officer) there for each inmate," Myers said.

- Reach Greg Gross at ggross@yorkdispatch.com.