The truthers are back.

Architects & Engineers for 9/11 Truth is paying for a 15-second ad to be broadcast on 300 TV screens in Toronto’s subway stations until April 1, promoting its belief that the collapse of World Trade Center Building 7 on Sept. 11, 2001, was due to a controlled demolition.

It’s a story that has been heard many times before, even though the official investigation says it was falling debris from the nearby Twin Towers that ignited fires in Building 7 and ultimately caused it to collapse.

Just last year, the American group, which says more than 2,100 architects and engineers have signed a petition calling for an independent investigation into the building’s demise, placed a billboard in Yonge-Dundas Square urging passersby to at least consider their version of events.

The latest “ReThink911” ad campaign coincides with an 18-city Canadian speaking tour by one of the group’s members, architect Richard Gage. He will be in Toronto Thursday evening at the University of Toronto’s Innis Town Hall.

“We think that the families (of the victims) deserve justice. We’re not here trying to upset anybody,” said Gage, who prefers not to be labelled a “truther,” but rather a “patriotic American” sounding the alarm.

“What we’re trying to do is raise a red flag, because if there’s any question about what happened on 9/11, which created two wars and the loss of our civil liberties and massive economic hardship to the people of Canada and America, then we’ve got to get to a real investigation and answer these questions.”

Who would have been behind this controlled demolition is still up for discussion, said Gage.

The video itself simply shows two different shots of Building 7’s collapse, which a hurried commuter — as in most commuters — could easily miss as they rush for the subway. Architects & Engineers for 9/11 Truth raised $75,000 for this ad campaign as well as a similar one involving posters on Ottawa buses.

TTC spokesman Brad Ross said he highly doubts the video violates the commission’s advertising policy, which prohibits ads inciting hate or violence, or contravenes the Ontario Human Rights Code.

He said if the TTC receives five public complaints about the campaign, a board subcommittee will undertake a review to determine if staff appropriately applied the advertising policy for ReThink911.

As of Tuesday afternoon, one complaint had already been lodged, by Gordon Yarley, who tweeted his displeasure at Ross. The Toronto resident saw the ad on Reddit.

“Someone saying they want to spark a discussion is fine, but you’re talking about a crazy conspiracy theory which, even if it turned out to be magically true, it would just open up fresh wounds for all involved,” Yarley told the Star.