Ticket sales for the hotly anticipated Toronto run of the hit Broadway musical The Book of Mormon broke down just as they began this morning after the sales website came under pressure from extraordinary demand and unusual online activity that the show's local presenter blamed on foreign scalpers using sophisticated software to push themselves to the front of the line.

Within minutes of the 11 a.m. kickoff of sales, the website for Mirvish Productions effectively seized up, while fans trying to buy tickets over the phone said their calls simply rang repeatedly without any answer. Ticketking.com, which sells tickets for Mirvish shows, served up a potpourri of error messages – "505 – Internal server error," "Your order could not be filled," "Server timed out."

Frustrated theatre fans took to Twitter and other social media to angrily chastise the company for its apparent lack of preparedness for the sales, which had been stoked by heavy advertising in the past couple of weeks. The show is only in Toronto for six weeks, with no chance for a possible extension. It has played to standing-room-only houses since opening on Broadway almost two years ago.

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Mirvish Productions blamed the chaos on a combination of heavy demand and automated software programs deployed by scalpers that hit a website with a barrage of requests for access, severely hampering a site's ability to process traffic from regular buyers. The effect is similar to so-called Denial of Service attacks used by hackers to disrupt websites that displease them.

"No amount of server space would solve that problem," said John Karastamatis, a Mirvish spokesperson.

Mirvish Productions had tried to prevent the activity by taking the unprecedented step of denying tickets to anyone who is not a legal resident of Canada, and enforcing a limit of eight tickets per credit-card holder. "It's impossible to get away from them," Karastamatis said.

Still, he said the main problem was simple: "There's a bottleneck. Tickets are still being sold, it's just a matter of being patient." He added that the Mirvish Twitter account was trying to respond to frustrated buyers with a direct link to the page on the Mirvish site where they could buy tickets.

But even theatregoers who went the old-fashioned route, lining up in front of the Princess of Wales Theatre in downtown Toronto, were upset. The best tickets available on her date of choice for Katie Schramm, who was first in line at 5:30 a.m., was in Row F of the dress circle – the first balcony. "Disappointing to wait for 3 hrs in the cold & not have many options," she told The Globe and Mail over Twitter. She was joined by more than 100 others who hoped to buy tickets in person before they went on sale over the phone and online.

While Mirvish trumpeted today as the first on-sale date, tens of thousands of tickets for the show's limited run have already been sold. Mirvish says it has about 40,000 subscribers – all of whom had first crack at the tickets as part of their subscription package – and American Express cardholders also had three days last week to purchase tickets, through that company's Front of the Line incentive program.

Mirvish said subscribers did not have access to the show's sixth and final week of tickets. "We've done everything we possibly can to make sure no one is left out," Karastamatis said. "It's an incredibly popular show."