BRUSSELS, Belgium (AP) -- Infineon, STMicro and NXP said Wednesday they were among several chip makers raided by EU antitrust investigators seeking evidence of a cartel that fixed the prices of chips for bank and identity smart cards.

The European Commission said it launched surprise raids on the offices of smart card chip manufacturers in several European nations on Oct. 21.

It did not name the companies but said it had reason to believe they had violated EU rules that outlaw price-fixing, customer sharing and swapping commercially sensitive information.

Germany-based Infineon Technologies AG confirmed that it had been visited. Spokesman Kay Laudien said the company would "fully contribute to clarifying" regulators' queries.

NXP, formerly the semiconductor arm of Royal Philips Electronics NV, said it had been quizzed by antitrust officials and was cooperating with the investigation.

Switzerland-based STMicroelectronics NV also confirmed that regulators had visited their offices.

Regulators said the raids did not mean the companies were guilty and the companies would have a chance to defend themselves before the EU decides on charges.

Antitrust fines can run as high as 10 percent of a company's global turnover for each year that it broke the law -- often landing businesses with multimillion euro penalties.

Smart card chips are used in telephone cards, bank cards, social security and identity cards.