Brussels: The EU opened an in-depth probe into alleged collusion by major German carmakers over anti-pollution technology on Tuesday, a fresh blow to the scandal-hit industry three years after the notorious “dieselgate."

Competition Commissioner Margrethe Vestager said BMW, Daimler and VW are suspected of agreeing “not to compete against each other on the development and roll-out" of anti-pollution systems for petrol and diesel passenger cars.

“If proven, this collusion may have denied consumers the opportunity to buy less polluting cars, despite the technology being available to the manufacturers," she added.

The probe lands three years to the day after shock revelations following a United States investigation that VW installed software in millions of its diesel vehicles around the world to cheat emissions tests.

The latest case does not involve these so-called “defeat devices", but instead focuses on alleged delays in the deployment of state-of-the-art control systems that reduce smog-causing pollution, such as nitrogen oxides and particulate matter.

The Commission said the probe was working with evidence of meetings and collusion by a group it called the “circle of five": BMW, Daimler, Volkswagen, in addition to VW units Audi and Porsche.

The commission said that the “circle of five" discussions also involved other subjects including crash tests and top speeds for cruise control, but these did not “at this stage" show evidence of collusion.

Contacted by AFP, the companies said that they will cooperate with the investigation.

A Daimler spokesman said the company had put itself forward as whistle-blower in the case, a special status that if accepted would allow for leniency by the EU authorities.

BMW affirmed “its full commitment to the principles of free market and fair competition," adding that the group is itself investigating the charges.

And Volkswagen suggested that the opening of the investigation represents only a “procedural step", which was entirely expected by the group.

The price of collusion can be dear. In 2016 and 2017, Brussels slapped its biggest ever cartel fines totalling nearly four billion euros on Europe’s top truckmakers, accusing them of colluding to fix prices and dodge the costs of stricter pollution rules.

The probe comes at a sensitive time for VW, which faces a raft of court cases in the coming months over its pollution test cheating.

These include several courtroom rebellions by shareholders, who say they were told too late about the cheating.

Investors are seeking compensation for the losses they suffered after VW’s share price plunged by 40 percent when the cheating was revealed in September 2015.

VW insists that the cheating was carried out by a small group of engineers without superiors’ knowledge.

“On the third anniversary of Dieselgate, this new investigation into collusion between German carmakers ... is a timely reminder that German car industry puts profits above people and the law," said Greg Archer of the European environmental NGO Transport & Environment.

Marking the anniversary, the NGO released a report alleging that 43 million “dirty diesels" remain on Europe’s roads.

“The number of grossly-polluting diesel cars and vans on our roads has increased by five million since last year and is up 14 million on when the Dieselgate cheating was exposed on this day three years ago," it said.