The decision to launch an investigation, announced on Friday, followed raids at the companies in several EU countries more than two years ago. Businesses found guilty of violating EU rules could be fined up to 10 percent of their global turnover.
The European Commission's action comes as the industry continues to grapple with overcapacity in a faltering global economy.
The Commission said in a statement that it is concerned that the companies appeared to be alerting each other of their price increases via press releases and on their websites. Such concerted practices are illegal under EU antitrust rules.
"The Commission has concerns that this practice may allow the companies to signal future price intentions to each other and may harm competition and customers by raising prices on the market for container liner shipping transport services on routes to and from Europe," it said.
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