An investigation is underway after multiple overdoses at Sarnia Jail.

Emergency crews were called to the facility on North Christina St. just before 5pm Friday. When Sarnia Fire and Rescue Arrived they found three inmates and one guard overdosing on an opioid.

Firefighters performed an emergency decontamination and two more guards were added to the list of those heading to hospital for treatment.

OPSEU Local 128 President Joel Bissonnette says a quick response from everything involved saved lives.

"Another reminder of how serious the crisis in corrections is right now," he says. "We have Narcan kits available to help with someone who is experiencing overdose and our job is to maintain care until we can get them to the hospital."

Sarnia Mayor Mike Bradley says he asked the province to declare an opioid crisis a month ago.

He wants more transparency.

"All the information should be out there so the public understands what happened, last night had the potential to be a major tragedy," he says. "Hopefully this a wakeup call for the Ontario government to take care of the jail system, to make sure our guards are protected and to make sure drugs aren't entering the system."

Bissonette said that's easier said than done.

"Inmates are going to look for ways to circumvent our tools. There's no 100 per cent guaranteed way to ever prevent everything from getting in," says Bissonette.

He says the inmates and guards involved have been treated and released from hospital.