TORONTO (CP) -- Airlines, railways, bus and light rail systems across Canada stepped up their security precautions Thursday after a series of deadly explosions on London's transit system killed dozens of people and injured hundreds more at the height of the daily commuter crush.
The early-morning blasts prompted officials across the country to tighten security on everything from international airline flights to crosstown subway lines, Public Safety Minister Anne McLellan told a news conference in Edmonton.
Tighter security measures for transportation systems were put in place after last year's deadly train bombings in Spain, which claimed the lives of 190 commuters.
''There is no specific threat to Canada or Canadians at this time, but you have to be prepared, you have to take all precautionary measures,'' McLellan said.
Few officials were willing to discuss the specifics of their security measures, but at Toronto's sprawling Pearson International Airport, K-9 units increased their patrols, while additional security guards were called in at railway stations across Canada.
From Montreal to Vancouver, bus, subway, and light rail operators were also on high alert.
In Toronto, transit officials issued a ''vigilance notice'' to staff in the middle of the morning rush hour and doubled the number of security personnel for the afternoon commute. But Toronto Transit Commission chairman Howard Moscoe conceded that public transit systems are limited in their ability to prevent a terrorist attack.
''It's extremely difficult to prevent, there's no doubt about it,'' Moscoe said.
''There's several hundred unattended parcels that are left on the TTC by shoppers every year. Every one of those could possibly have an incendiary device in it ...our staff watch people rather than parcels.''
Commuters in Canada's most populous city were largely unaware of the notice and said the overseas bombings, which erupted several hours before they began heading to work, didn't change their daily routine.
''I didn't see the advisory, but I think there's a pretty low probability of something like that happening here,'' said David Crombie, a Toronto businessman, as he exited the downtown King Street subway station.
''Even if I had, it wouldn't have changed my habits.''
Iain Newbigin, a marketing manager with Soulpepper Theatre Company, said he appreciated the advisory.
''I suppose it shows due diligence on the part of the TTC,'' Newbigin said as he walked out of a subway stop.
In Montreal, police sharpened their surveillance on the subway, commuter trains and city and regional buses.
''Following the events that happened in London this morning, we immediately increased the police presence in places of interest, for example all public transport networks,'' said Montreal police spokeswoman Anie Lemieux.
''Nothing makes us believe we are threatened for the moment.''
Amped-up security did not make Eric Meunier, a Montreal commuter, feel any safer.
''It's a waste of public funds,'' Meunier said. ''There's nothing that can be done. If they want to attack, they will attack.''
The SkyTrain, an elevated rapid transit system which operates in and around suburban Vancouver, added more security personnel as a precaution.
Edmonton Transit also increased security at the city's bus and light rail system.
''We've heightened our level of awareness of our security personnel and our supervisors,'' said Wes Broadhead, director of bus operations.
''What was different about London was that a bus was involved as well. That was of concern to us. Our staff have been asked to be more vigilant.''
City transit officials in Ottawa, however, chose not to take any extra security steps.
''There is no current change to our activity level,'' said John Ash, manager of the emergency measures unit for the City of Ottawa. ''Obviously, staff have to be vigilant as on any other day.''
Four explosions rocked London's subway system and tore open a packed double-decker bus during the morning rush hour Thursday, sending bloodied victims fleeing in the worst attack on the city since the Second World War.
At least 37 people were killed and more than 700 injured.
Cherie Traverse, a spokeswoman for the federal Public Safety Department, said Ottawa has urged transit authorities to increase their state of alert and request operators to report any unusual occurrences.
''The government of Canada has been in touch with Canada's major transit authorities and operators to update them on the attacks and to promote higher alert status for transit operations across Canada,'' Traverse said.
''Major rail and commuter train operators have also been alerted, and have been advised to increase vigilance.''
Canadian airlines were also being advised to take extra care on flights from the United Kingdom to Canada, she added.
Newbigin said the blasts reminded him of how cavalier transit riders in Toronto can be.
''Thinking back to the Irish terrorism in the '70s . . . British transit authorities were always saying, 'Be on the lookout for unattended parcels, unattended briefcases,''' Newbigin said.
''In Toronto, if we saw something unattended we'd assume it had been lost rather than it was a bomb.''