Ontario Provincial Police say an investigation is underway after cannabis chocolate cake brownies were served at seniors' community luncheon.

It happened in Whitestone, Ont., a community of about 900 people located 40 kilometres northeast of Parry Sound.

Police say they were called after several people "required medical attention" after going to the luncheon.

After speaking with those involved, police say only those who ate the chocolate cake brownies were affected.

Police say 10 people required medical attention, as they were dizzy, disoriented and some experienced nausea and vomiting.

OPP Constable Miles Loach says part of the police investigation will be to determine where the brownies came from.

"These luncheons are catered," he said.

"It's still part of the investigation whether that was what happened [that] somebody brought the wrong batch or somebody spiked them."

Police say there is no information that anyone suffered any serious or lasting effects from consuming the brownies.