HARRISBURG — Pennsylvania’s state prisons are on lockdown after employees at an eighth prison in recent weeks required treatment from exposure to a yet-unidentified substance described as a liquid synthetic drug.

The Department of Corrections announced the step Wednesday, a couple hours after it reported that two guards and three nurses at Albion state prison became sick.

Pennsylvania is now reporting 29 employees getting sickened starting Aug. 6 in eight western and central Pennsylvania prisons. Symptoms include dizziness, lightheadedness, nausea and skin tingling.

The medical emergencies began earlier this month at the state Prison in Mercer County. Five corrections officers and a doctor from the facility were rushed to Grove City Medical Center via ambulance, and the medical center put into quarantine after they came into contact with an unknown substance while searching cells in the facility’s restrictive housing unit. GCMC was shut down for about two hours and a decontamination was set up outside, where the victims were treated.

About a week later, six staff members at Butler County Prison — four COs and two nurses — were rushed to Butler Memorial Hospital under similar circumstances. In the wake of that incident officials at the jail say they have revised policies and procedures to improve safety. Warden Joe DeMore has said the unknown substance is suspected to be K2, also known as synthetic marijuana. The substance is often smuggled into prisons and jails after being sprayed in liquid form on letters and the pages of books. It’s use by prisoners has been connected to violent episodes in prisons across the state.

The state Department of Corrections says it doesn’t know how long the lockdown will last.

In the meantime, it’s suspending prison visits, closing mailrooms to non-legal mail and requiring all employees to use gloves and other protective equipment.

Prison staff also is to use extra caution with parole violators and newly arrived inmates.

From staff and wire reports