Normal operations resumed Monday at all Pennsylvania state prisons after a 12-day lockdown prompted by drug exposures that sickened multiple employees and inmates, according to the state Department of Corrections.

Update 11:15 a.m. EDT Sept. 10: Between May 31 and Sept. 1, more than 50 staff members and 33 inmates reported being sickened and were taken to hospitals, officials said.

In multiple cases of staff exposure, toxicology results confirmed the presence of cannabinoid, officials said. Lab tests confirmed inmate overdoses were linked to synthetic cannabinoids and other illegal substances.

Statewide mandatory training was enforced during the lockdown on wearing and removing gloves. Some team members were also trained in the detection, containment and removal of hazardous materials, according to the Department of Corrections.

“I am proud of our staff and how they all pulled together as a team,” Corrections Secretary John Wetzel said in a statement. “The safety of our staff is paramount to the running of this prison system, so we took this time to calm the system and to train staff so they can remain safe while performing their jobs.”

Wetzel said officials worked to ease some of the stress on inmates and their families by allowing some phone contact during the lockdown.

“We also communicated regularly with inmates to explain the reasons for the lockdown and our plans moving forward,” Wetzel said. “Our plans improve the safety of our system for both staff and inmates.”

Original report: All Pennsylvania state prisons were placed on immediate lockdown Wednesday after multiple unknown substance exposure incidents were reported across the system.

The lockdown came on the same day that two dozen inmates, guards and jail staffers were hospitalized in Ohio after being exposed to an unidentified substance at the Ross Correctional Institution.

“The safety and security of our employees is my No. 1 concern,” said John Wetzel, secretary of the Pennsylvania Department of Corrections. “Our state prisons, especially those in the western part of the state, have experienced recent incidents in which employees have been sickened and we need to get to the bottom of this issue now.”

During the lockdown, all prison mailrooms are closed to nonlegal mail, all visits are suspended, all employees will be required to wear protective equipment, including gloves, and all employees will undergo new training.

In a statement, officials with the Pennsylvania State Corrections Officers Association praised the decision.

“Simply too many of our officers are becoming sick due to contraband being illegally brought into these facilities,” the statement said. “We’re prepared to help our members who have been sickened — but we must put this dangerous problem to an end. It’s our hope the steps being taken today will do just that.”

WPXI has covered at least five of these incidents since mid-July:

The Cox Media Group National Content Desk contributed to this report.