12/29/2011 08:04 EST | Updated 02/28/2012 05:12 EST

Mercier Bridge to South Shore closed completely

The South Shore-bound lanes of the Mercier Bridge will be closed completely Thursday, leaving drivers scrambling for alternate routes.

Workers are doing maintenance operations on one side of the bridge underneath the span.

Transport Quebec was originally going to allow traffic to pass in both directions on the Montreal-bound side, but are now saying that was an error and there was a misunderstanding with the contractor.

Cynthia Martin with Transport Quebec said she couldn’t explain why South Shore-bound traffic couldn’t share the open side.

The South Shore-bound lanes are scheduled to re-open Friday at 5 a.m. Transportation officials are asking drivers to use the Champlain or Jacques-Cartier bridges instead.

They’re also asking drivers coming into Montreal from the South Shore on the Mercier to observe the speed limit and watch out for workers.