They do that out of respect to the victims' families and so to ensure that the immediate focus is on recovery and clean-up efforts.
Both the Liberals and New Democrats did just that two weeks ago during the floods in Alberta.
NDP leader Thomas Mulcair, however, has deviated from this tongue-biting convention.
On Saturday — just hours after the deadly train derailment and subsequent fires in Lac-Mégantic, Quebec — Mulcair said it was "another case where government cost cutting in the wrong area."
"We are seeing more and more petroleum products being transported by rail, and there are attendant dangers involved in that. And at the same time, the Conservative government is cutting transport safety in Canada, cutting back the budgets in that area," Mulcair said accordingRead More »from When tragedy strikes, should opposition leaders bite their tongues?