The offices of several Quebec cabinet ministers were vandalized in Montreal early Monday in an hour-long vandalism rampage in what appears to be the latest manifestation of student anger related to rising tuition costs.

Windows were smashed, Molotov cocktails were thrown and red paint was splashed on the offices.

The city's underground Metro system was also targeted.

Overnight several government offices were targeted, including those of the justice minister, the labour minister, the finance minister and the minister in charge of seniors.

Red squares were also painted on the sidewalks nearby.

"The student groups themselves, most of them are denouncing the acts of violence and saying they don't condone the acts of violence but at the same time you have whoever is doing this using the red square which is a symbol of the students," CTV Montreal's Aphrodite Salas told CTV News Channel.

The office of the minister responsible for seniors, Marguerite Blais, was evacuated after a suspicious substance was found inside.

"When we arrived, there were already police here and we went in by the back door and when we went in the office, we smelled a strange odour and the police decided to call the firefighters," office manager Gabriel Retta told The Canadian Press.

"They said it's a bottle, so maybe it's a Molotov cocktail," he said.

The Metro system was also bogged down after the vandals threw bags of bricks onto the system's tracks, said Metro spokeswoman Isabelle Tremblay. Emergency brakes were pulled in five different stations stopping the trains for about half an hour.

Several people were arrested Monday morning at a CEGEP not far from where the vandalism occurred. Two 19-year-old men were arrested just after 5 a.m. and charged with breaking and entering, while a third 19-year-old male was arrested later and charged with mischief.

"Since these events all happened at the same time we're talking about what seems like a concerted act, so in this case an investigation has been opened by the Montreal police department," said Anthony Cantelmi, a Montreal police spokesman.

A police spokesperson said two provincial investigators have been called in to help with the probe.

Police would not say if particular student groups were being investigated in relation to the Metro disruption.

No one was hurt in the violence, but at least one building had to be evacuated.

Student walkouts and demonstrations have disrupted classes and traffic in recent weeks in Montreal.

On Friday, seven people were arrested after a group broke into and vandalized Education Minister Line Beauchamp's Montreal office.

More mass protests are planned for Wednesday, Friday and Sunday across the city.

Still, the Liberal government has extended an olive branch to the students, with an invitation to talk about how universities are managed, but that invitation didn't go out to all the student groups.

And leaders from the main student group that was not invited to the table -- Coalition large de l'association pour une solidarité syndicale étudiante (CLASSE) -- say they are skeptical about the proposed talks.

"Madame Beauchamp will probably try to talk about the management of our universities without talking of the main issue of the strike which is the tuition increase. But we want to remind Madame Beauchamp that those issues are completely related -- that it will be in fact impossible to talk of one without talking of the other," said CLASSE spokesman Gabriel Nadeau-Dubois.

Indeed, student leaders say the level of frustration is rising.

"I don't think the subway or the bridge are the right targets for the students. We should concentrate our pressure on the Liberals; on Quebec's government. That should be our main target," Leo Bureau-Blouin, the head of Quebec's Federation of College Students.

With a report from CTV Montreal