OTTAWA, May 10 (Reuters) - The subway system in Montreal, Canada's second-largest city, was partially shut down on Thursday after someone set off smoke bombs in several stations during the morning rush hour, police said, without attributing blame for the attacks.
City police found three smoke bomb devices after receiving dozens of calls about dense smoke in some underground stations. Thousands of commuters were stranded, but nobody was hurt.
Disrupted subway services were gradually being restored later in the morning.
Montreal has been the epicenter of large student protests, some of them violent, as students complain about proposed tuition hikes. The students have shown little sign of standing down even after the Liberal provincial government offered them to compromise.
Police have made no link between the smoke bombs and the student protests, and have called on the public to help with their investigation by sending in any photos or videos that may have been taken on mobile phones.
"There are five teams of investigators...on the field right now to try to establish exactly who did this," said Simon Delorme, media officer at the Montreal police. (Reporting By Louise Egan; Editing by Janet Guttsman)