An internal report by the STM revealed that half of interruptions were caused by passengers. One of last year's major interruptions was the result of several smoke bombs that sent the transit service into chaos at the peak of rush hour last May.
Other causes of service delays included technical problems like computer glitches.
Executive director of the Metro system, Dominique Lemay said blasts from construction sites close to metro lines also caused issues.
He said they were forced to stop the service more than 60 times to allow for blasts related to the construction of Montreal's new French-language superhospital on René Lévesque Boulevard.
Lemay said the STM will gradually begin replacing it's aging fleet of metro cars in the fall of 2014.