By Edward Welsch

Of Dow Jones NEWSWIRES

CALGARY -(Dow Jones)- Suncor Energy Inc. (SU) pleaded guilty Friday to conspiring with competitors to fix the price of gasoline in Belleville, Ont. and will pay a C$500,000 fine, Canada's Competition Bureau said.

Suncor is a 50% joint-venture partner in a retail gasoline station operated by Pioneer Energy L.P. in Belleville and for several months in 2007 employees of the two companies improperly shared information on gasoline prices, the Competition Bureau said.

"Our representative understood the rules barring competitor collusion, but they believed they did not include Pioneer because they were a 50/50 owner in that joint venture," a Suncor spokeswoman said.

No other Suncor stations were involved in the price fixing.

Pioneer Energy was also fined in a separate price-fixing case last month in the nearby towns of Kingston and Brockville, Ont. All three towns are in eastern Ontario and near the U.S. Canadian border.

In that case, Pioneer and retail outlet Canadian Tire Corp. (CTC.A.T) also pleaded guilty to gasoline price-fixing and paid nearly C$1 million in fines each.

-By Edward Welsch, Dow Jones Newswires; 403-229-9095; edward.welsch@dowjones.com