Montrealers using the métro system will see an increased police and transit authority security presence on their station platforms after a trio of smoke bombs shut down the system on Thursday.

Société de transport de Montréal chairperson Michel Labrecque said the transit authority’s security force also would be more visible, and STM employees had been told to be on the lookout for any suspicious behaviour.

The measures were announced after three homemade smoke bombs were detonated within minutes of each other at around 8 a.m. Thursday, forcing a series of station shutdowns that eventually resulted in the entire network’s being stalled until about 10:30 a.m.

The smoke bombs detonated in the tunnels adjoining the Prefontaine, de Castelnau, Lionel-Groulx and Fabre stations, apparently after being hurled from the station platforms and into the adjoining tunnels.