There was a release of a light hydrocarbon Wednesday morning at Imperial's Sarnia site.
Sirens sounded at 6:40 a.m. and again just after 7 a.m following the release from a section of piping in the chemical plant.
Imperial said, as a precaution, a Chemical Valley Emergency Coordinating Organization (CVECO) Code 6 was issued and traffic control by the Sarnia Police Service was requested.
Vidal Street South between Clifford Street and Kenny Street was closed, so was River Road at LaSalle Line and Highway 40 from LaSalle Line to Churchill Line.
The all-clear was issued around 8:20 a.m.
Company spokesperson Kristina Zimmer said the Ministry of Environment has been notified and air monitoring is being conducted.
No injuries have been reported.
