Several makers of heavy electrical equipment have been sent formal charges by the European Commission alleging they fixed prices for "gas insulated switchgear" used in power substations.
Siemens of Germany and Swiss engineering group ABB acknowledged in May 2004 that they had been raided in relation to such equipment.
The commission, without identifying the companies, said today that those raids had led to the charges.
"The European Commission can confirm that it has recently sent a statement of objections to a number of undertakings regarding their alleged role in a cartel for gas insulated switchgear," it said in a statement.
The commission said the companies involved had fixed prices and allocated contracts in the European Economic Area, which includes the 25-member European Union and three other countries.
Gas insulated switchgear is heavy, expensive equipment that controls the flow of energy. It is sold as a distinct product and as part of fully functional power substations.