Police have now removed the cordons they put around a street in central Invercargill after reports of a strong chemical smell.
They were called to the boarding house in Tyne Street about 2pm.
Police cordoned off the street and evacuated some houses, and helped move students away from the nearby St Joseph's school.
The Fire Service confirmed to police the smell had come from someone using cannabis oil.
The cordons have been removed but police are still looking for the culprit.