Pennsylvania's 25 state prisons were put on lockdown Wednesday as officials try to come to grips with a growing drug smuggling problem that is causing staff sicknesses and growing numbers of assaults.

In all, prison system officials said 29 staffers at eight different prisons have been treated for overdose-related or other symptoms since Aug. 6. In at least three of the incidents, the overdose antidote Narcan was administered.

Preliminary investigation suggests in many of the cases the sicknesses may have resulted from incidental contact with smuggled drugs or other illegal substances, and not intentional or coordinated attacks on the system.

Nonetheless, the growing risk - including incidents at two Pennsylvania prisons that affected six DOC staffers Wednesday and a similar incident affecting one inmate and 23 staffers at a prison in Ohio - have unnerved prison staff to the point where emergency action was required.

"The safety and security of our employees is my number one concern," Corrections Secretary John Wetzel said in a release announcing the lockdown. "... We need to get to the bottom of this issue now."

Maryland wasn't taking any chances. That state's Department of Public Safety and Correctional Services temporarily suspended visits at correctional institutions in response to prison staffers in other states needing treatment. A department statement on Wednesday said there will be no prison visits until further notice. Also, mail will be accepted at prison but not opened or distributed. Prison staffers have been advised to use all provided protective equipment.

Pennsylvania's extraordinary system-wide lockdown means inmates will be confined to their cells and housing units around the clock, and all visitations to the prisons have been suspended.

Prison mailrooms will not be processing any non-legal mail.

Typical was this incident at SCI Greene on Aug. 13:

Four corrections reported feeling ill while searching an inmate's property. The area and the officers were isolated to prevent the further spread of the possible contaminant, and the employees were eventually taken to a local hospital for evaluation.

Wednesday morning, results from Pennsylvania State Police tests of material recovered from the search tested positive as a synthetic cannabinoid. It's the only case to date where testing has been completed.

Sold on the street as "Spice," or "K2," the drugs are manmade compounds that some push as an alternative to marijuana, but they can cause serious side effects that are very different from those of marijuana.

Those effects can be exacerbated - and create dangers even from incidental or secondary contact - by cutting agents like fentanyl or other opioids that are sometimes added to the mix.

In the Ohio incident, a hospital official said Wednesday afternoon that the patients were likely exposed to fentanyl.

The staff sicknesses have also coincided with a notable uptick in the number of drug smuggling incidents, officials said, both in in-person visits and through letters and other items of mail.

DOC had logged six contraband discoveries systemwide since Saturday in incident reports shared with Wednesday's announcement.

"Smuggling drugs into prison is nothing new," Press Secretary Amy Worden noted Wednesday. "But this particular drug is very easy to smuggle in," sometimes secreted under stamps or even saturated into paper itself.

Wetzel's move was immediately applauded by some lawmakers and the president of the Pennsylvania State Corrections Officers Association, which represents some 10,000 state prison employees.

"Too many of our officers are becoming sick due to contraband being illegally brought into these facilities," PSCOA President Jason Bloom said in a statement released by the union.

"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."

But an attorney who has specialized in fighting for fair and humane conditions in the prisons said Wednesday he was concerned by the sweep of the lockdown over what seems to be a set of isolated incidents.

Besides Greene, prisons affected by the recent rash of incidents include the State Correctional Institutions at: Mercer, Smithfield, Camp Hill, Fayette, Rockview, Albion and Somerset.

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Angus Love of the Pennsylvania Institutional Law Project said his objection is that this is "punishing 48,000 people for the sins, if there were any, of a few. I'm not sure that is the right approach."

Wetzel was not available for an interview Wednesday.

But DOC officials have said they are taking the following steps to address the problems:

Requiring the use of protective gloves by all employees.

Installing body scanners at all institutions to run checks following inmate visits to capture possible drug transfers.

Upgrading mail processing capabilities to better detect and divert contraband. One possibility under consideration is giving inmates copies of all letters, instead of originals.

According to DOC figures, the system is also been battling an uptick in inmate-on-inmate and inmate-on-staff assaults this year, which officials also attribute to increased drug trade within the prisons.

The staff assault rate grew by 4 percent from last year through the first six months of 2018, DOC said, with 657 attempted or actual assaults logged across the system through Aug. 20.

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The Associated Press contributed to this report.