Montreal police have released photos of four suspects linked to a co-ordinated smoke-bomb attack that shut down the city's metro system during the busy Thursday morning rush.
The images of three women and one man were made public hours after the subway sabotage, that stranded thousands on their way to work.
In all, three stations had smoke bombs thrown onto their tracks between 7:45 and 8:30 a.m.
Officials shut the stations down, and eventually closed the entire metro network at the height of the morning rush.
It isn't clear whether the incidents were intended as part of ongoing protests against tuition rates in the province.
But Mayor Gerald Tremblay asked Montrealers to "take back their city" following the incident.
"No cause, legitimate or not, can justify any criminal action that jeopardizes public security," said Tremblay during a heated press conference.
Quebec Premier Jean Charest also condemned the attack.
"It's inexplicable," Charest told reporters in Gatineau, Que. "There's no reason to commit acts of intimidation and violence. There's no excuse for this -- none."
The shutdowns resulted in a major headache for anyone trying to use Montreal's transit system to get to work.
The first reports of problems came in around 8 a.m., forcing commuters out into the open air and triggering the shutdown of the entire system by 8:50 a.m. as officials tried to vent the smoke, said CTV Montreal's Derek Conlon.
He described the situation as "rush hour mayhem" following the closure of the city's green, blue, orange and yellow lines.
"There are hundreds of people standing out here in the street not knowing where they're going or what they're doing," Conlon reported.
Buses were rerouted to help carry passengers to their destinations, but there were too few to fully disperse the massive crowds of stranded commuters, Conlon said.
In some cases, people attempted to hitchhike to work, and there were reports of Good Samaritans picking up stranded commuters at Metro stations.
By 11 a.m., all four lines were once again operating with "no significant disruptions," according to the Societe de transport de Montreal (STM) website.
In the past month there have been several instances of transit disruptions due to smoke bombs. Conlon said it's too early to say whether Thursday's incidents, which appear to be co-ordinated, were politically motivated.
