Government of Canada advertising was supposed to stop the moment Stephen Harper called the election on Sunday, but it could take up to five days to cancel all publicity, according to a notice on advertising posted by the Department of Public Works and Government Services Canada.

That would help explain why an anti-drug ad purchased by Health Canada was still airing in prime time Monday night during the evening news on Radio-Canada, CBC's French-language counterpart — or why an ad from Heritage Canada promoting Canada's 150th birthday was still running on television on Tuesday.

"As soon as the election was called, the government of Canada contacted its media-buying agency and instructed them to contact all media outlets to cancel all government of Canada advertising," said the notice on advertising during the federal election posted on the Public Works website.

And depending on where the ad was placed, "it can take up to five days to cancel advertisements."

The notice was posted on Aug. 3 — the day after the election was called — by Public Works, which is responsible for contacting the agency that purchases the ads.

"TV advertisements should all be pulled within the next 48 hours," the notice said.

All stations were informed as soon as the election was called. However, since Monday was a holiday for some stations, some spots ran Monday and Tuesday. –Simon Rivet, Department of Canadian Heritage spokesman

The federal health agency spent $1.5 million to run the ads on TV and online until Aug. 8, but on Wednesday, it could not say whether the anti-drug ad had been pulled from all platforms, referring CBC News to Public Works.

However, Alexandra Fortier, a spokeswoman for the public broadcaster said on Wednesday the ad was no longer airing on CBC/Radio-Canada.

Also, a spokesman for Heritage Canada confirmed to CBC News on Wednesday that Public Works "removed all the government of Canada ads" including the TV ads promoting Canada's 150th birthday.

"All stations were informed as soon as the election was called," said Simon Rivet, a media relations officer for the Department of Canadian Heritage.

"However, since Monday was a holiday for some stations, some spots ran Monday and Tuesday," said Rivet in an email to CBC News.

Monday was a statutory holiday for many workers in a handful of provinces, including Ontario.

'Result of delays'

A different notice posted on the main government of Canada website acknowledged that it wasn't just government of Canada ads that should have ceased with Harper's election call on Sunday, but also news releases touting government announcements including funding investments.

"It has come to our attention that some government of Canada news releases and supporting social media were shared on Monday August 3, 2015," said the government notice posted on a page that was edited Wednesday.

Some news releases and notifications only appeared online today as a result of delays in posting regular web updates over a long weekend. -–Notice posted on the government of Canada website

For instance, a statement by Rona Ambrose in her capacity as health minister was issued on Monday announcing that she had "directed Health Canada to create a task force to crack down on illegal marijuana advertising."

"Some of these government of Canada announcements were made before the election was called," the government notice said.

It appeared to clear government MPs for announcements being issued after the election was called, noting it's the responsibility of public servants to post the information online.

"Some news releases and notifications only appeared online today as a result of delays in posting regular web updates over a long weekend. News releases and notifications by government of Canada departments are posted by public servants," the government of Canada notice said.

Exceptions apply

While most government ads will stop running soon enough, some exceptions may apply, said a spokesperson for the Treasury Board of Canada Secretariat pointing to the following examples.

Advertising during a general election is only permitted when:

An institution is required by statute or regulation to issue a public notice for legal purposes.

An institution must inform the public of a danger to health, safety or the environment.

An institution must post an employment or staffing notice.

"Otherwise, advertising plans and activities … must not resume until the day the newly elected government is sworn into office, said Lisa Murphy, a media relations spokeswoman for the Treasury Board, in an email to CBC News on Wednesday.

On Thursday, the Treasury Board told CBC News in an email the agency responsible for buying the ad space had "confirmed all government of Canada advertising has been cancelled."​

While Canadians will stop seeing any further government ads during the election period, the real barrage of political ads by federal parties and third-party organizations has only just begun, as CBC reported on Monday.