A monthly community lunch for a group of Ontario seniors took a strange turn this week after many attendees got sick from consuming cannabis-laced brownies, provincial police said Thursday.

Const. Miles Loach said the seniors began seeking medical help within less than an hour of eating chocolate brownies served as a dessert option at the catered gathering at the community centre in Whitestone, Ont., about half an hour east of Parry Sound, Ont.

"There was 10 that went to our health centre because of the symptoms of being high," Loach said in a telephone interview. "They did tests on them and found that it was marijuana that they were high on."

Loach said police received a call shortly before 6 p.m. on Tuesday after the flurry of arrivals at the local health centre.

He said one by one, lunch attendees reported feeling symptoms ranging from dry mouth to dizziness to disorientation. A few even reported nausea and vomiting, Loach said.

Puzzled by the spike in people reporting similar symptoms, Loach said investigators began asking questions about the day's activities. It wasn't long before a pattern emerged.

"We got a hold of everybody who was at the meeting and the only people that had these symptoms were the ones that ate the chocolate ... brownies," he said.

Loach said the dessert was one of the offerings served at the gathering, which typically functions as a social opportunity for the community's elderly residents.

He said police are now actively investigating to see how the cannabis-laced brownies made their way on to the menu.

Loach said that if anyone at the catering company or beyond is determined to have spiked the brownies on purpose, they could find themselves facing a charge of administering a noxious substance.

He said no such determination has yet been made, however, and the investigation remains open.

None of the seniors appeared to recognize the symptoms of cannabis at the time, Loach said. Nor did they suffer any lasting effects of their unexpected high, he said.

"Thank goodness nobody was injured," he said. "Because if somebody had been allergic or got in their vehicle and drove and had an accident and killed somebody or whatever, then we'd be facing a whole different set of charges."