Quebec's transport minister says the government will claim damages from the crane operators' union for the costs of a strike that has paralyzed work sites across the province.

Andre Fortin says in a statement that he's planning to send a formal notice to the union over what he describes as an illegal strike.

Most of the crane operators remain off the job for a fifth straight day despite a labour board ruling ordering them back to work.

In granting the interim order on Thursday, the tribunal ruled that the urgency to act was justified because the strike was having a significant impact on work sites. Fines for disobeying the order can reach as high as $10,000 for an individual and $100,000 for a union. 

Quebec Construction Association spokesperson Guillaume Houle said the strike is costing millions of dollars while delaying both private and public works.

"It's a big problem for our construction sites and for entrepreneurs," he said. "We encourage entrepreneurs to call on the authorities to denounce the situation right now."

The operators are protesting changes made to training requirements that will allow workers to operate cranes without first obtaining a vocational diploma.

Crane operators say the new training program is less comprehensive and could lead to a rise in workplace accidents.

According to the association, there have been some operators turning up to work, includings sites in Quebec City.