MONTREAL -- There could be some major changes in the plans for the REM light-rail line in Montreal, as officials want a downtown portion of the line to go underground.

The Caisse de Depot, which is putting the project together, said Thursday that the downtown portion of the line heading east and north will include an underground tunnel beneath Rene-Levesque Blvd. from Robert Bourassa station to the intersection of Jeanne-Mance St./Rene-Levesque Blvd. intersection.

It's the newest adjustment to the REM de l'Est to avoid an elevated track all the way down the major Montreal artery.

Concerns have arisen that the tunnel is not long enough and that the Jeanne-Mance and Rene-Levesque intersection would be closed causing a major nuisance for drivers on the busy section of road.

Promotors of the project, however, see the tunnel as being a major bonus to maximize efficiency in the public transit systems.

"You can connect with every line of existing subway including the future REM," said Caisse president Jean-Marc Arbaud. "That's, I believe, the main advantage."

Studies were done on the feasibility of making the tunnel even longer, but concerns about cost and delays mean that's no longer on the table.

Montreal Mayor Valerie Plante's administration wants to see more studies done.

"We have a lot of challenges for urban integration of the REM de l’Est," said executive committee member Eric Alan Caldwell. "Those studies, the effort that we must put to find other solution, to study them, to price them has to be done for all the REM de l’Est."

Many groups are concerned about the train's aesthetic appeal, and worry it could scar the city's image.

"I have to say we support the project but we are asking many questions about the urban integration," said Quebec Urban Planners Order's Sylvain Gariepy.

Gariepy isn't just worried about downtown, but also about other parts of the city like Sherbrooke and Notre-Dame streets.

"The structure will remain above ground and that is a concern for us," he said. "How will it look like, how will it impact the quality of life of the people that living on those streets?"

UQAM professor Nathalie Drouin is an expert in project management and said social acceptability is a key issue, but building a project that attracts people can help.

"What does it mean to build national pride," she said. "It means also having an innovative and very beautiful design. I’m not sure we’re there yet."

The project will be studied by Quebec's environmental review board in 2022.