VANCOUVER -- Police suspect the "unknown substance" that left families with red and burning skin at a Mission, B.C. water park this week was bear spray.

On Wednesday, Cpl. Nathan Berze said authorities are still piecing together what happened at the Mission Leisure Centre around noon on Tuesday, but that they are treating the incident as criminal.

"I have never heard of an incident ever happening like this in Mission," Berze told CTV News. "We're really eager to find out exactly what went on here."

One witness posted on social media that young children were crying from the burning sensation in their eyes and mouths caused by the unidentified substance.

Authorities said at least 15 people, including both parents and kids, were affected. Paramedics and firefighters treated most of them at the scene, but one patient spent a short time in hospital.

"We're still trying to identify other victims that may have been involved," Berze added. "We're asking those people to come forward and speak with us."

Mission RCMP said samples of the substance have been sent to a forensic lab for testing. It's unclear who used the suspected bear spray or how it was deployed, but Berze said investigators are "following up on every available avenue."

The District of Mission quickly closed the park down after the incident and has already tested the water, but found no irregularities there, including in the chlorine levels.

Mounties said anyone with information on what happened can call the Mission detachment at 604-826-7161 or Crime Stoppers.