The benchmark index of the Toronto Stock Exchange tumbled nearly 3% on Wednesday as lower commodity prices dragged energy and materials stocks lower.

The S&P/TSX composite index dropped 298.67 points, or 2.8%, to close at 10,290.12.

The energy group plummeted 4.8% as oil futures dropped. Crude for July delivery fell US$2.43, or 3.5%, to US$66.12 a barrel on the New York Mercantile Exchange, after news that oil inventories unexpectedly increased last week.

Shares of Suncor Energy Inc. dropped $2.19, or 5.8%, to $35.74.

Petro-Canada fell to $45.00, down $2.38, or 5%.

Shares of Canadian Natural Resources Ltd. tumbled 6.1% to $62.50 and Canadian Oil Sands Trust plunged 6.9% to $26.90.

Also sharply lower was EnCana Corp., down 4.3% to $59.98, and Talisman Energy Inc., down 4.6% to $16.69.

The materials group on the TSX finished down 3.9% after gold futures slipped lower. Gold for June delivery fell US$18.70, or 1.9%, to US$964.50 an ounce on the Comex division of the New York Mercantile Exchange. The sub-gold index shed 3.5%.

Shares of Goldcorp Inc. dropped $1.89, or 4.5%, to $40.31.

Kinross Gold tumbled 6.5% to $21.19 and Yamana Gold Inc. fell 5.2% to $12.13.

Teck Resources Ltd. retreated 5.9% to $17.60.

Shares of Agrium Inc. plunged 5.4% after it said it had extended its US$4.1-billion bid for CF Industries Holdings Inc. to midnight June 22. Agrium shares fell $2.88 to $50.05.

Financial stocks shook off 2.3% on Wednesday.

Manulife Financial Corp. fell 4.1% to $23.22 and Sun Life Financial Inc. ended at $29.55, off 3.2%.

Bank of Nova Scotia fell $1.15, or 2.9%, to $38.70.

Also lower was Royal Bank of Canada, off 2% to $44.01.

The consumer discretionary group was the only main group on the TSX to advance during Wednesday’s trading, edging up just 0.1%.

Shares of Bombardier Inc. fell 8.5% after the company reported that profit fell to US$158 million for the first quarter of fiscal 2010 as the recession caused weakness in the firm’s aerospace division. Bombardier shares fell $0.33 to $3.54.

The junior S&P/TSX Venture composite index tumbled 3% on Wednesday, finishing at 1,107.96, down 33.78 points.

Meanwhile, a boost in the U.S. dollar sent the loonie down a sharp US2.29¢, to close at US90.22¢.

In New York, U.S. stocks also retreated on Wednesday as U.S. Federal Reserve Board chairman Ben Bernanke revealed expectations that lower economic growth may persist for some time, and that longer-term fiscal challenges lie ahead.

The Dow Jones industrial average shed 65.63, or 0.8%, to end at 8,675.24.

The S&P 500 index fell 12.98 points, or 1.4%, to close at 931.76.

The Nasdaq composite index fell 10.88 points, or 0.6%, to 1,825.92.

IE