BRUSSELS: The EU's competition regulator said on Monday that it has been investigating a number of liquid crystal display supply firms on suspicion that they might have been involved in a cartel.

"The European Commission can confirm that in May 2009 it sent a statement of objections under EU antitrust rules to a number of companies active in the supply of liquid crystal display (LCD) panels," a statement said.

The statement of objections -- a first formal step in antitrust probes -- was made "concerning their alleged participation in a cartel in violation of (EU) rules on restrictive business practices", it said.

The companies being probed were not named. They can respond to the statement of objections in writing, laying out the elements of their defence, or request an oral hearing to present their case.

Liquid crystal display panels are used in calculators, mobile telephones, digital watches and cameras, televisions and computers.