According to post to the Ligne Orange Twitter account, the line is currently shut down between Snowdon and Lionel-Groulx stations.
A "train breakdown" is to blame, though the STM has not released any further details. At the time of writing, service is expected to resume at 2:10 PM.
UPDATE: The STM now projects that service will not resume until 2:20.
In fact, passenger actions are the leading cause of metro service interruptions. It is for that reason that the STM has launched three separate campaigns in the past six months to advice customers on how to avoid delay-causing behaviours.
UPDATE: Service is now resuming on the Orange line.
The latest campaign is a revival of the much-maligned "conseils de Michèle," featuring Michèle Deslauriers, the voice of the Montreal metro.
Before today, June 5, the last major orange line service interruption was on June 3. Earlier this year, the orange line went an impressive 27 days without a shutdown.
Stay tuned. We will update this article with more information when it becomes available.