The European Commission on Tuesday said it has launched surprise inspections of tyre companies in several EU countries after suspicions of price collusion.
France's Michelin, the US's Goodyear and Germany's Continental were among companies confirming they'd been inspected.
The commission, the 27-country bloc's powerful antitrust authority, said it was "concerned that price coordination took place amongst the inspected companies".
It did not name the firms nor say in which countries investigators -- joined by competition authorities of each member state affected -- had conducted raids.
French firm Michelin said it was inspected but was quick to deny involvement in any anti-competitive practices.
Michelin denied "categorically the existence of anti-competitive practices such as those evoked by the European Commission it its statement today, and therefore any price collusion activity," a spokesman told AFP in a statement.
A Continental spokesman told AFP: "We can confirm that investigations by European antitrust authorities are taking place at Continental in Germany since today."
Goodyear also said there had been inspections at its European sites.
"It is too early to speculate on what exactly may have happened, but we are fully cooperating with authorities," the company told AFP.
Nokian Tyres also confirmed the inspection at its headquarters in Nokia, Finland, and said it was "fully cooperating with the authorities".
"Nokian Tyres does not have information on the outcome of the inspection, and it cannot comment on the ongoing investigation," Nokian said on its website.
Other major tyre manufacturers didn't immediately respond to requests for comment.
The inspections do not mean the companies are considered guilty of anti-competitive behaviour.
The products involved are new replacement tyres for passenger cars, vans, trucks and busses sold in the European Economic Area (EEA), the commission said in a statement.
The EEA includes the 27 EU member states as well as Iceland, Liechtenstein and Norway.
The commission is probing claims that the companies violated EU competition rules that prohibit cartels and restrictive business practices.
If the firms inspected are later found guilty of antitrust violations, they risk large fines but can be granted immunity if they cooperate with the commission.
There is no legal deadline by which the commission must complete its investigation.
The announcement hit the shares of tyre companies.
Stocks in Continental fell by around two percent to 75.40 euros a share on the Frankfurt stock market towards 1615 GMT, while Michelin shares were down 0.9 percent to 30.80 euros on the Paris stock exchange.
Michelin denies anti-competitive practices after EU raids
Michelin denied engaging in any anti-competitive practices after the European Commission on Tuesday launched surprise inspections of tyre companies in several EU countries following suspicions of price collusion.
The French firm denied "categorically the existence of anti-competitive practices such as those evoked by the European Commission it its statement today, and therefore any price collusion activity," a spokesman told AFP in a statement.