Luxembourg has launched criminal proceedings over Volkswagen’s diesel emissions scandal, showing the German carmaker is still struggling to draw a line under the crisis some 17 months after it broke.

The European Union country said on Monday that following investigations it was taking legal action against “unknown persons” over the EA 189 engine made by Volkswagen’s (VW) Audi division.

The engine, which was tested and certified by Luxembourg authorities, was used in most of the cars that VW has admitted in the United States included illegal “defeat device” software that could conceal the true level of toxic emissions in tests.

“We have decided that, as there is a large probability that a defeat device was used, to launch a lawsuit against unknown persons,” Luxembourg’s infrastructure minister, François Bausch, told journalists.

Investigations across the world are still trying to identify all the individuals involved in the scandal.

Bausch’s ministry described itself as “a victim of criminal action that led it to certify cars,” adding it would not have done so had tests not been falsified.

Spokespeople for Audi and VW declined to comment. In late trade, VW shares were down 2.2 percent at 141.69 euros.

Luxembourg is one of seven EU countries under scrutiny by the European Commission, which feels member states have not done enough to crack down on emissions test cheating.

VW, Europe’s biggest carmaker, admitted in September 2015 to using software to rig U.S. diesel emissions tests and said the software could be in up to around 11 million vehicles worldwide.

In the United States, the company has agreed to spend up to $25 billion to address claims from owners, environmental regulators, U.S. states and dealers, and offered to buy back about 500,000 polluting vehicles.

In Europe, officials in some countries say it has been difficult to ascertain whether VW has done anything wrong because of a loophole in EU law which allow carmakers to dial down emissions control systems under some circumstances, such as if they might damage a vehicle’s engine.

Nonetheless, several countries continue to investigate the matter and other interest groups are also taking legal action.

Fish distributor Deutsche See said on Sunday it was suing VW for misrepresenting a fleet of vehicles it leased as environmentally friendly, becoming the first major German customer to sue VW over the emissions scandal.

(Reporting by Michèle Sinner; Additional reporting by Andreas Cremer and Jan Schwartz.; Writing by Alissa de Carbonnel.)