Quebec's construction commission is seeking an order from a labour tribunal that would force the province's crane operators back to work.
The tribunal began hearing arguments from both sides of the conflict today.
Crane operators are protesting changes to the training program for new workers and have been off the job since Monday, crippling construction sites across the province.
The construction commission, which enforces labour rules in Quebec, says the strike is illegal because crane operators are under contract until 2021.
There are 1,856 crane operators in the province and 1,573 of them are represented by two major unions.
The dispute is rooted in changes made last May allowing workers to operate cranes without getting a vocational diploma.
Local 791-G, affiliated with the Quebec Federation of Labour's construction wing, argues the new program is less comprehensive and could lead to a rise in workplace accidents.
