In a notice issued on Sunday, Aamjiwnaang First Nation Band Council said all buildings closed due to high benzene levels will reopen on Monday, April 29.
The first nation said levels were monitored regularly over the weekend, and again all buildings are opening Monday.
However, should benzene levels exceed 27 micrograms per cubic metre at a specific location, buildings in the area will be closed once again.
Last Thursday, the First Nation declared a state of emergency to assist in preparedness and ensure adequate resources are available in the event that further action is required.
The band office has been closed since April 16, when staff complained of headaches, nausea and dizziness due to high levels of benzene in the air.