Buildings in the area of Aamjiwnaang's sportscentre air monitoring system were closed on Monday.
The First Nation reported through its notification system just before 3 p.m. that high benzene levels were detected in the area off Tashmoo Avenue.
Aamjiwnaang advised staff in the band office, blue building, environment building, child and family services building, education administration building, CIDL, public works and the church to leave the area immediately.
The buildings were to be closed for the remainder of the day on Monday and the First Nation said they would stay closed on Tuesday, November 19.
Staff were advised to work from home, unless managers asked them to report to the community centre or another location.