Mexico's antitrust watchdog said Wednesday it confirmed fines for 419.1 million pesos ($31.5 million) against the Ferromex and Ferrosur railway companies for price fixing.

The Federal Competition Commission, or CFC, said the fines are against the two railway concerns and the companies that own them - copper miner Grupo Mexico (GMEXICO.MX), conglomerate Grupo Carso (GPOVY) and a unit of Grupo Financiero Inbursa (GFINBUR.MX).

The fines followed an unauthorized 2005 merger of Ferromex and Ferrosur, which operate two of the country's three privatized railways. The other railway is run by the local unit of Kansas City Southern (KSU), which has opposed the merger.

The CFC said that since it hasn't authorized the merger, from a legal standpoint Ferrosur and Ferromex continue to be competitors and are therefore "subject to competition laws as independent companies."

A spokesman for Ferromex said the companies involved plan to contest the fines in court.

Under the merger of the two railways, Carso and Inbursa sold Ferrosur to Grupo Mexico for a 25% stake in Grupo Mexico's transport unit ITM, which includes both railways.

The dispute over the merger is also being fought in court.

-By Anthony Harrup, Dow Jones Newswires; (5255) 5001 5727; anthony.harrup@dowjones.com