Nine staff members at the Minnesota Correctional Facility in Stillwater were treated at a hospital and released Thursday after being exposed to a synthetic drug, according to the state Department of Corrections.

The staffers reported feeling lightheaded and nauseous with increased heart rates, the department said in a news release. Eight staff members were taken to Lakeview Hospital in Stillwater by paramedics, and one was administered Narcan.

The incident began at about 7:45 a.m., when a staffer began feeling ill after responding to a report of an incarcerated man smoking an unknown substance in his cell. A short time later, three other staffers who had responded to the man began feeling sick, and two of them went to the hospital.

In a separate incident in the same housing unit, another incarcerated man threw a container of an unknown substance that landed near three staffers, who then began feeling ill and were taken to the hospital.

Investigators have not yet identified the substance, officials said. The man caught smoking in his cell told investigators that it was a stronger-than-expected dose of K2, or synthetic marijuana.

At a news conference Thursday, Corrections Commissioner Paul Schnell acknowledged that synthetic cannabinoids have a problem at the Stillwater prison, which houses men, and other prisons across the state and nation.

Jeff Vars, president of AFSCME Local 915, the union that represents corrections workers, said in a statement that an incarcerated man at the Stillwater facility and another at a medium-security prison in Moose Lake had died from suspected overdoses in the last week.

"Our union has asked repeatedly and fought for many years to seriously and meaningfully address incoming mail and property to limit any potential drugs from coming into the facility to protect staff and offenders alike, but our ideas have been ignored," Vars said.

It was reported Wednesday that the Federal Correctional Institution in Waseca, a low-security facility for women, has been on lockdown for two weeks after nine residents were hospitalized for potential drug use, along with two staffers who were potentially exposed.

A 2023 report by the U.S. Department of Justice said the facility has faced challenges limiting drugs and other contraband from entering the population.

"This is a national issue that's affecting corrections across the board," Schnell said.

He added that synthetic cannabinoids can now be liquified and soaked into paper without leaving watermarks, which can then be mailed to residents and smoked. The drugs also may enter corrections facilities with the help of staffers who smuggle them in.

About a month ago, the Stillwater prison began a pilot project to photocopy residents' mail and provide the photocopies, rather than the original materials, to the recipients. Schnell said that practice has resulted in a reduction of incidents.

Star Tribune staff writer Jp Lawrence contributed to this report.