An explosion inside the Mount-Royal tunnel on July 20 suspended all work on the réseau express métropolitain (REM) as a century-old explosive discharged.
No one was injured in the blast and officials say there was no fire.
But an investigation was held and new measures are now required using remote controlled equipment instead of workers in certain instances.
Deterioration of tunnel walls under McGill College Avenue and the coronavirus pandemic have all led to delays in delivering the project.
The entire mass transit system is not expected to be ready until the fall of 2024.
READ MORE: Montreal gets sneak peek of new stations on West Island REM lines
Significant cost overruns are also anticipated — pushing the project well above the $6.3 billion budget.
“We are continuing to estimate what is going to be the impact of this cost,” Macky Tall, the CEO of CDPF Infra, said during a press conference.
Plans to extend the REM station at the Trudeau Airport to the Dorval train and bus terminal still haven’t been finalized.
“Studies are being conducted by transport Canada. We’re participating in those studies and we will see what the conclusion is,” Tall said.
Officials can’t guarantee the REM will meet its new target day in the autumn of 2024.