The European Commission (EC) has informed a number of suppliers of smart card chips of its preliminary view that they may have participated in a cartel, in breach of EU antitrust rules.
The EC send a statement of objections to suspected companies, but did not identify the firms.
Infineon Technologies and NXP Semiconductors have previously said they are cooperating with the Commission's investigation. Renesas Technology and STMicroelectronics have confirmed the regulatory raids.
The sending of a statement of objections does not prejudge the outcome of the investigation.
The EC has concerns that certain chips suppliers may have agreed or coordinated their behaviour in the European Economic Area (EEA) in order to keep prices up.
The EC initially agreed to explore the possibility of a settlement with the companies involved but has now discontinued the talks due to lack of progress. The normal antitrust procedure will now run its course.