* TSX erases gains, down 0.3 percent, at 13,349.63
* Index on track for 4th straight down day (Adds details)
By Ka Yan Ng
TORONTO, May 13 (Reuters) - Toronto's main stock index reversed early gains and was lower on Friday afternoon as commodity prices, notably oil and gold, dropped after data showed U.S. inflation hit the highest level in 2-1/2 years.
Commodity prices had been steady early in the day and helped push up the market. But oil then tumbled and gold dropped about 1 percent as the U.S. dollar rose on safe-haven buying.
At 1:45 p.m. (1745 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 39.79 points, or 0.3 percent, at 13,349.63, after falling for three straight days. Eight of its 10 sectors were lower, with the financial group down about 0.4 percent.
Major U.S. stock indexes were down about 1 percent.
"There's clearly some massive positions being closed. Risk is being unwound," said Francis Campeau, broker at MF Global Canada, in Montreal.
"We're finishing the week similar to how it started."
The energy sector was down 0.6 percent. Suncor Energy (SU.TO), dropped 0.64 percent to C$38.63, while Canadian Natural Resources (CNQ.TO) fell 0.9 percent to C$39.65. Nexen NXY.TO slid 2.8 percent to C$21.60.
($1=$0.97 Canadian) (Reporting by Ka Yan Ng; editing by Peter Galloway)