It was the kind of thing officials always take seriously – but never more so than now.

So when a call came in to authorities threatening something on the subway, they didn’t take any chances. And if you were on the system Thursday morning, it caused you a lot of trouble and inconvenience.

Cops won’t say what was in the call they received, but it's effect was immediate. The subway was shut down around 9:50am from Eglinton station all the way down to Union on the Yonge line and from St. George to Chester on its Bloor-Danforth counterpart.

Thousands of morning commuters interrupted their journeys to leave every station and head upstairs for hastily assembled shuttle buses.

It didn’t take long before those vehicles were jammed and the roads soon followed, as the extra traffic swelled already burdened post-rush hour roads.

Full service finally returned to normal just after 11am.

Authorities are especially sensitive to any danger and have deboubled security efforts, after a recent series of bombings on the London transit system claimed more than 50 lives earlier this month.

But while Canada has been named by al-Qaida as a potential terrorist target, there was no sign that anything dangerous actually took place on Thursday, and the system is safe to ride.