The investigation into the manufacturer of Citroen and Peugeot cars follows similar probes into Volkswagen, Renault, Fiat Chrysler and Opel. The investigations are the wake of Volkswagen's 2015 admission that it used "defeat device" software in 11 million cars that allowed it to give false results in tests for nitrogen oxide emissions.
A probe was opened into PSA Group earlier this month in relation to alleged consumer fraud offences, a court official told Reuters.
PSA Group agreed to buy Opel and Vauxhall from General Motors last month.
PSA also announced a long-term partnership in automotive finance with BNP Paribas in relation to Opel/Vauxhall'ss financing activities. The two will jointly acquire all of GM Financial’s European operations through a newly formed 50% / 50% joint venture that will retain GM Financial’s current European platform and team, it said. The joint venture will be fully consolidated by BNP Paribas and accounted under the equity method by PSA.
The European Commission began legal action in December against seven member states over emissions cheating in the 'dieselgate' scandal.
European countries must have "effective, proportionate and dissuasive penalties systems in place to deter car manufacturers from breaking the law. Where such a breach of law takes place, for example by using defeat devices to reduce the effectiveness of emission control systems, these penalties must be applied," the Commission said.
In June 2016, Germany called on the EU to improve rules on vehicle emission testing to cover the range of adaptations to emissions control systems used by vehicle manufacturers.
While no other manufacturer was using a similar system to Volkswagen's, "it became clear that for many vehicle types, real driving emissions are significantly higher than on the dynamometer", Germany told the European Transport Council.