TORONTO – Canada’s main stock index closed lower Tuesday amid reports of a major selloff from an unknown international dealer, even as U.S. markets rose.“From about 10:30 this morning a big sell program came in internationally at one of the dealers,” said Dominique Barker, Portfolio Manager, CIBC Asset Management.“We don’t know which one, but the market has sold off, and the Canadian dollar also sold off from about that time. So that’s impacting the Canadian market versus the rest of the world.”The Toronto Stock Exchange’s S&P/TSX composite index closed down 133.94 points at 16,286.30 in a broad-based decline following a selloff that hit most of the TSX-60 names. The index hit an intraday high of 16,494.09.The S&P/TSX capped materials index declined the most, down 1.45 per cent, while the healthcare sector was the only index see gains with a 0.08 per cent rise. Volume for the Toronto Stock Exchange as a whole came in at 338.23 million.Barker said lower volumes on the TSX may have made the selloff have an outsized impact.“This is summer volume time as well, so you tend to have a little bit less volume, so something like that could have a larger impact on the day.”The dip in the TSX comes in the midst of what has generally been quite a positive earnings season, said Barker.“Earnings reporting has exceeded expectations generally, the economy is very strong.”The source of the selloff is unclear, but it comes after Saudi Arabia has responded forcefully through economic and political means to criticism from Canada’s Global Affairs Ministry about the arrest and detention of two female bloggers and activists in the kingdom.Saudi Arabia has declared a freeze on new trade with Canada and recalled thousands of students attending Canadian universities following the tweet last week from Global Affairs Canada.The Saudi foreign ministry has also ordered Canada’s ambassador, Dennis Horak, to leave the country. Saudia Airlines has also announced it will suspend flights to and from Canada starting Aug. 13.SNC-Lavalin Group Inc., which has a major presence in Saudi Arabia, closed down $1.97 or 3.48 per cent at $54.56. The company issued a statement saying it greatly values its contributions to the Kingdom Saudi Arabia over the past five decades, declining further comment.The Canadian dollar also took a sharp drop in the later half of the day to average 76.79 cents US Tuesday, down 0.23 of a US cent.The strength of the U.S. dollar also played a role on the shift in the currency, said Barker.Stock performance in Toronto was in contrast to New York, where the Dow Jones industrial average closed up 126.73 points at 25,628.91, the S&P 500 index ended up 8.05 at 2,858.45 and the Nasdaq composite index was up 23.99 points at 7,883.66.The September crude contract closed up 39 cents at US$68.33 per barrel and the September natural gas contract was up four cents at US$2.90 per mmBTU.The December gold contract closed up 60 cents at US$1,218.30 an ounce and the September copper contract ended down two cents at $2.75 a pound.