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PITTSBURGH (KDKA) — Synthetic drugs are believed to be the cause in a rash of illnesses among Pennsylvania prison employees.

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About 29 employees at nearly a dozen facilities across the state have gotten sick in just the past month.

Employees in Greene, Mercer, Fayette and Somerset counties were among those sickened.

Officials believe the employees were likely exposed to K2, a synthetic form of marijuana. It comes in a clear, odorless liquid form that can be sprayed on letters or book pages inmates receive in the mail. The inmates can then ingest or smoke the paper.

The substance can cause confusion, anxiety and paranoia.

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“What we’ve really been doing is putting a push on making sure staff are trained in using the protective equipment,” Pennsylvania Corrections Secretary John Wetzel said.

All 25 Pennsylvania state prisons are currently on lockdown, which means inmates cannot see visitors and won’t get any mail until prison personnel can undergo hazmat training.

“Our long-term solution for that is to switch to scanning all mail. We’re working with a vendor right now to try and seal that as quickly as we can,” Wetzel said.

The lockdown is in effect indefinitely.

“I’m sure we’ll modify and start getting a little different out-of-cell time, but certainly visits and mail will be the last things that come back online until we get up and running,” Wetzel said.

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Some prison employees were hospitalized, but they have since recovered and been released. At least four more employees at SCI Somerset became sick Thursday evening despite the lockdown after they found inmates smoking.