The Ontario Environment Ministry continues to investigate a rotten egg smell that came from the Sarnia Suncor refinery last Thursday.
The odour was caused by the release of total reduced sulphur compounds, which includes hydrogen sulphide, and various mercaptans.
Ministry spokesman Gary Wheeler says the compounds aren't generally considered a health hazard at low concentrations.
He says air monitoring showed the odour began to dissipate after an hour.
The ministry still hasn't decided whether to refer the matter to the enforcement branch for the possible laying of charges.
Anyone impacted by the incident is asked to call the ministry's Public Pollution Reporting Hotline at 1-866-663-8477 or the Sarnia office at 519-336-4030.