A prisoner and four employees at the Calgary Correctional Centre had to be rushed to hospital after coming in contact with a mysterious powder.

At around 5 p.m. Saturday, a guard noticed one of the inmates had some sort of powder, but wasn’t sure what it was. The prisoner and two correctional officers then suffered a physical reaction to the substance.

Paramedics brought those three—along with two other prison workers—to hospital. All five have since been released.

“The substance appears to have been introduced into the institution by the inmate, who is back at the centre,” Jason van Rassel, spokesperson for the Alberta Justice and Solicitor General, wrote in a statement.

“Fire and hazmat response were requested as a precautionary measure because the substance was an illicit drug that could not be identified. Centre staff acted quickly to contain the situation with the support from multiple Calgary emergency services personnel."

The incident remains under investigation.

This isn’t the first case of Alberta prison guards needing medical attention after coming in contact with an unknown substance at their prisons.

In mid-July, six prison guards at the Edmonton Institution came into contact with fentanyl. Two were taken to hospital, and one required naloxone, a medication that reverses the effects of an opioid overdose.

The escalating number of fentanyl overdoses across the country has prompted many front-line emergency responders to carry naloxone kits in case a patient needs the life-saving medicine.

At the Bowden Institution just outside Red Deer, a correctional officer was hospitalized for 48 hours after being exposed to fentanyl.

Guards come into contact with fentanyl when conducting searches, performing CPR on inmates and sorting through mail, among other ways.

The union representing the correctional officers will be meeting Monday to discuss a plan of action to present to the province to ensure corrections officers have the tools they need to stay safe on the job.

In early August, CTV Edmonton reported the union wanted to see changes in prison rules when it comes to dealing with unknown substances. Police officers take additional precautions when dealing with one gram of a potential drug, but for correctional officers, the threshold for additional precautions is three grams.

With a report from CTV Edmonton