At a publicity appearance in Toronto, Canada, last week the management had to pull the plug halfway through an interview because of safety concerns.
The number of fans at their MuchMusic performance even dwarfed the last appearance from Canada's own Justin Bieber.
There were 17,000 requests for tickets from 1D fans, compared with 4,000 when Bieber made his last homecoming appearance on Canada's answer to MTV.
Just over a year ago 1D were third place on The X Factor, now the Brit band are toppling Bieber Fever in his own backyard.
Speaking from his 14th floor Albany hideout while working his way through autographing 3,000 pictures, teen heart-throb Harry said: "They had to close off the streets in Toronto, it was crazy.
Read more at http://www.thesun.co.uk/sol/homepage/showbiz/bizarre/4169159/Bizarre-on-tour-with-One-Direction-in-US.html