(Adds details on specific stocks, updates prices)
* TSX down 71.18 points, or 0.46 percent, at 15,471.96
* Half of the TSX's 10 main groups fall
* Energy stocks down 2.7 pct, materials stocks off 1.8 pct
TORONTO, May 4 (Reuters) - Canada's main stock index fell in morning trading on Thursday as the country's heavyweight energy and mining sectors lost ground amid a drop in commodity prices and as investors digested a string of corporate earnings.
Oil prices fell to the lowest since a November OPEC deal, while gold hit a six-week low and copper extended losses after its biggest one-day drop in 20 months.
Canada's energy group, which accounts for more than a fifth of the index's weight, retreated 2.3 percent.
Its materials sector, another major weight which includes precious and base metals miners and fertilizer companies, lost 1.9 percent.
Canadian Natural Resources, the country's largest independent petroleum producer, fell 3.8 percent to C$41.61 after reporting a first-quarter profit, compared with a loss a year earlier.
TransCanada Corp fell 1 percent to C$63.34 after saying it would sell stakes in two pipelines for $765 million.
Diversified miner Teck Resources Ltd lost 6 percent to C$25.03 after Deutsche Bank lowered its price target in the stock, while Hudbay Minerals fell 8.7 percent to C$7.15 after reporting an unexpected quarterly loss.
At 10:21 a.m. ET (1421 GMT), the Toronto Stock Exchange's S&P/TSX composite index was down 71.18 points, or 0.46 percent, at 15,471.96.
Manulife Financial Corp rose 1.6 percent to C$24.52 after Canada's biggest life insurer reported first-quarter earnings that exceeded expectations with strong sales in Asia.
Canadian Imperial Bank of Commerce fell 1.2 percent to C$107.81 after it raised its offer for PrivateBancorp .
Home Capital Group Inc fell 1.2 percent to C$6.76 after the DBRS ratings agency downgraded the stock, following two downgrades last month, as it reviewed the alternative mortgage lender's ongoing viability.
The overall financials group gained 0.3 percent.
Empire Company Ltd, parent of Sobeys grocery chain, was up 1.7 percent at C$20.78 after announcing a restructuring plan it says would deliver C$500 million of savings a year by 2020. (Reporting by Alastair Sharp; Editing by Bernadette Baum)