The European Commission Wednesday fined six companies for colluding in the power transformers market.

Swiss ABB Ltd. (ABB), France's Areva SA (CEI.FR) and Alstom SA (ALO.FR) and Japan's Fuji Electrics Co Ltd. (9883.TO), Hitachi Ltd. (HIT) and Toshiba Corp. (6502.TO) were all found guilty and fined for having put in place an oral market sharing agreement, where the European and Japanese power transformer makers promised to stay out of each others' markets.

Germany's Siemens AG (SIE.XE) also participated in the agreement, but wasn't fined as it had revealed the existence of the cartel to the commission.

Power transformers are used to modify the voltage in electricity transmission networks.

The highest fine was given to Swiss engineering company ABB at EUR33.4 million, because the company had participated in a similar cartel before.

-By Peppi Kiviniemi, Dow Jones Newswires; +3227411483; peppi.kiviniemi@dowjones.com