A part of Sainte-Catherine Street W was first blocked off this afternoon as maintenance workers tried to replace a 128-year-old sewer pipe made of brick.
The Ville-Marie borough said workers have had to dig a hole into the street in order to access the old pipe which had collapsed.
"We're trying to do it the fastest we can," said Réal Ouellet, the crew's surpervisor.
While working on the original rupture, crews discovered a large hole where another sewer pipe should have been.
Borough officials said they are unsure whether this second pipe had previously collapsed or what has become of it.
Traffic will be blocked off on Sainte-Catherine Street W between Guy Street and Saint-Mathieu Street.
Pierce Street is also blocked off between De la Police Street and Sainte-Catherine.