Demonstrators gathered on Saturday outside a job fair at the city's convention centre, where businesses and workers were meeting to discuss opportunities in the natural resources sector.
Police spokesman Ian Lafreniere said at least one window was smashed and a flare gun was fired inside the building.
"We tolerate protests but not criminal acts like this, so we decided to break up the protest," Lafreniere said.
In a scene reminiscent of last spring's student protests, lines of riot police were used to break up the crowd and protesters who were arrested were held on city buses.
Just like a day earlier, authorities declared the demonstration illegal as soon as it began because no protest route had been given beforehand.
Lafreniere said 32 people were arrested for unlawful assembly, while three others could be charged for assault against an officer and another for handling stolen goods.
No one was seriously injured, he said.
The protesters, many wearing the red square associated with the student movement, said they are opposed to plans for new mining projects in northern Quebec.
Marie Lys, a 25-year-old from Montreal, said the demonstrations are in solidarity with the Idle No More movement.
"We want to keep our resources and protect the environment and the resources that we have belong first and foremost to aboriginal people," she said.
Lys argued the approach to northern development hasn't changed much since Premier Pauline Marois and her Parti Quebecois took power in last September's election. Former Liberal premier Jean Charest faced criticism from some environmental groups for his Plan Nord while he was in power.
A demonstration against Charest's plan last April, outside the same convention centre, ended with violent clashes between protesters and police.
"The PQ and the Liberals are the same, it's simply that Pauline Marois changed the name of the plan," Lys said.
At one point, protesters chanted "Charest, Marois — same fight!"
Martine Ouellet, Quebec's minister of natural resources, defended the PQ's plan at a party meeting in Drummondville, Que.
"We want sustainable development," she said.
"We want development that's respectful of the environment and communities."
The two-day job fair was organized by the Board of Trade of Metropolitan Montreal and featured top politicians and business leaders.
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