TORONTO (Bloomberg) — Canadian stocks had their biggest decline in two months as commodity producers including EnCana Corp. and Teck Cominco Ltd. dropped along with crude oil and copper prices, on concern that demand for resources will cool.The Standard & Poor’s/TSX Composite Index extended losses in the afternoon after minutes from US Federal Reserve policy makers said the risk of slower economic growth has “increased a little” in the US, Canada’s biggest trading partner. The minutes of the December 12 meeting also said inflation was “the predominant concern” as policy makers kept the benchmark interest rate at 5.25 percent.

“Commodity prices may weaken further,” said David Rea, chairman of Davis-Rea Ltd. Investment, which manages $382 million in Toronto. “The US economy is slowing. Profits will grow at a slower pace.”

The S&P/TSX dropped 222.22, or 1.7 percent, to 12,701.44 for its biggest decline since November 1. The benchmark advanced yesterday in the first day of trading in Toronto in 2007, and rose 14.5 percent last year.

Gauges of energy and raw-materials producers, which account for more than two-fifths of the value of the S&P/TSX, lost 3.4 percent and four percent, respectively.

Crude oil for February delivery dropped 4.5 percent to $58.32 a barrel in New York, the most in 20 months, as mild weather in the US curbed heating demand and traders speculated that fuel inventories increased. The price of oil is down 7.6 percent from a year ago.

EnCana, Canada’s, biggest natural-gas company, slipped C$1.14 at C$53.21. Smaller rival Canadian Natural Resources Ltd. retreated C$4.24, or 6.8 percent, to C$57.25.

Suncor Energy Inc. fell C$4.41 to C$86.61. The world’s second- largest oil-sands producer was downgraded to “hold” from “buy” by analyst Paul Sankey at Deutsche Bank.

Copper futures for March delivery plunged 7.7 percent to $2.649 a pound in New York, the most since June 13.