* TSX falls 47.81 points, or 0.31 percent, to 15,468.42
* All of the index's 10 main groups fall
* U.S. crude oil prices decline 0.9 percent
* Gold futures fall 0.6 percent
TORONTO, Sept 26 (Reuters) - Canada's main stock index retreated on Tuesday from a four-month high hit in the previous session, as a drop in commodity prices weighed on the shares of oil and mining companies.
The energy group, which has rallied more than 15 percent since late August, declined 0.4 percent.
Global oil prices struck a 26-month high but then fell on profit-taking. U.S. crude futures were down 0.9 percent to $51.75 a barrel. Shares of petroleum and gas pipeline operator Enbridge Inc fell 0.4 percent to C$50.84.
Regulatory hearings for the company's C$8.2 billion ($6.62 billion) Line 3 crude oil pipeline upgrade are to begin in the U.S. state of Minnesota, the last hurdle for the project.
The materials group, which includes precious and base metals miners as well as fertilizer companies, lost 0.4 percent as a pullback in the price of bullion weighed on gold mining stocks.
Gold futures fell 0.6 percent to $1,298.8 an ounce, with investors booking profits after rising tensions between North Korea and the United States pushed the metal to a one-week high.
Copper prices also declined, falling 0.6 percent to $6,413 a tonne.
At 11:35 a.m. ET (1535 GMT), the Toronto Stock Exchange's S&P/TSX composite index fell 47.81 points, or 0.31 percent, to 15,468.42.
All of its 10 main groups were lower.
The index posted on Monday its highest close since May 12 at 15,516.23.
Shares of Bombardier Inc retreated 2.3 percent to C$2.09 ahead of a U.S. trade court's preliminary ruling, expected to be made public on Tuesday, on Boeing Co's complaint that the company is dumping its new CSeries passenger jet in the U.S. aircraft market.
Still, the planemaker aims to close deals with Chinese airlines in time for an expected trip by Canadian Prime Minister Justin Trudeau to China next month, a senior Bombardier executive said.
The financials group, which accounts for more than one third of the index's weight, dipped 0.2 percent. Consumer staples shares were down 0.5 percent.
$1 = 1.2383 Canadian dollars Reporting by Fergal Smith; Editing by W Simon