It happened Wednesday night at a construction site adjacent to the Students' Union Building.
President Mike Mahon says the clean-up effort in the most affected areas is ongoing.
Those include the library, the Centre for the Arts and parts of University Hall.
Classes there will be relocated elsewhere and Mahon says the rest of campus remains operational.
So far there is no damage estimate but Mahon says insurance adjusters and restoration experts are on site.
(CJOC)Suggest a correction