The Toronto 2015 Pan Am organizing committee came up with the figure because they had to put something in the bid book that helped secure the international event for the city, said Tourism Minister Michael Chan.
"The $113 million was presented a long time ago, in 2010, and it was a place holder because security has to be there," said Chan.
"You probably will appreciate TO2015 doesn't have the skills, they don't have the expertise, they don't have any knowledge about security."
Saad Rafi, who took over as the CEO of the TO2015 Pan Am organizing committee after Ian Troop was fired, said he wasn't involved when the city's bid was prepared and couldn't say where the $113 million estimate came from.
Officials wouldn't have had a good handle on the number of athletes and coaches that would be coming or how many venues would be used and in what communities when they prepared the security estimate for the bid book, added Rafi.
"I think a myriad of elements and factors go into generating an estimate of costs," he said. "If you want a more detailed answer I'm afraid we couldn't give it because we weren't there to submit the bid book."
The Opposition demanded Chan resign or be fired after the security bill for next year's Games more than doubled.
"The minister and this government and TO2015 and everyone involved in these games doesn't have a clue what's going on," said Progressive Conservative critic Rod Jackson. "They can't answer a straight question in the House on this, and it seems like no cost is too high."
Chan bristled at suggestions he should have known what the original $113 million estimate for security at the Games was based on.
"I wasn't there," he said. "Do you really want to know why they had that number in there? There's probably a reason for that."
The $239-million tab for security will likely change before the Games start in July 2015, but could go down or up, added Chan.
"Anybody who thinks that number will be stationary, will not move, I think that would be unreasonable because we still have a year and five months before the Games and lots of things can happen," he said. "And that number can go down if we control costs, or security may go up. This is the nature of the Games."
Rafi announced the Games were on schedule and on budget so far, and admitted one of his biggest concerns was getting people interested in the Pan Am competitions.
"We want to engage the public and create a sense of excitement which will drive their participation in festivals as well as the Games themselves," he said. "We want to make sure we can maximize our ticket revenue."
The 2015 Pan Am Games will take place at 34 different competition venues across the Golden Horseshoe, from Niagara in the south to Orillia in the north, running from July 7 to 26, followed by the Parapan Am Games Aug. 7 to 15.
The total budget for the Games is now estimated at $2.5 billion.
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