Oct. 28 (Bloomberg) -- Shares of the following companies may have unusual moves in Canadian trading. Stock symbols are in parentheses.

The Standard & Poor’s/TSX Composite Index fell the most in three weeks yesterday, losing 181.34 points, or 1.6 percent, to 11,053.54.

Indigo Books & Music Inc. (IDG CN): Canada’s largest bookstore chain said it may buy back up to 1.23 million shares, or 5 percent of its outstanding stock, during the year beginning Nov. 2. Indigo has declined 8.1 percent since May 26.

Methanex Corp. (MX CN): The world’s largest methanol supplier said it had a loss of 1 cent a share in the third quarter, excluding certain items. Analysts were expecting profit of 17 cents a share, the average estimate of seven analysts surveyed by Bloomberg. The company said it had unplanned outages at plants in Chile and Trinidad.

Nexen Inc. (NXY CN): The oil producer with operations in Canada, Nigeria and the North Sea reported third-quarter earnings of 23 cents a share, excluding certain items, beating the average analyst estimate by 10 percent.

Opti Canada Inc. (OPC CN): Nexen’s partner in the Long Lake oil-sands project reported profit of 4 cents a share in the third quarter. Three analysts surveyed by Bloomberg had expected a loss of 9, 14 and 18 cents a share, respectively.

Progress Energy Resources Corp. (PRQ CN): The Western Canadian producer of oil and gas had its rating increased to “buy” from “neutral” by analyst Travis Wood of UBS AG after releasing the results of a resource assessment on part of its land in the Montney area of British Columbia.

Sherritt International Corp. (S CN): The diversified mining company reports earnings for the third quarter before the market opens. The average forecast of six analysts in a Bloomberg survey is for a profit of 13 cents, excluding certain items.

TransAlta Corp. (TA CN): Canada’s largest investor-owned power producer had its rating cut to “hold” from “buy” by analyst Linda Ezergailis of Toronto-Dominion Bank after reporting third-quarter earnings of 34 cents a share, excluding certain items, missing the average analyst forecast by 11 percent.

To contact the reporter on this story: Matt Walcoff in Toronto at mwalcoff1@bloomberg.net.

Last Updated: October 28, 2009 09:03 EDT