French anti-fraud detectives have raided production sites belonging to Renault in relation to a possible investigation into emissions cheating.

As a result, shares in the French company, which is partly-owned by the French state, dropped by 20.2% this morning, wiping nearly ?2bn off the manufacturer’s value. The share price has recovered this afternoon, but is still down on the opening price.

The share prices of other manufacturers were also hit as a knock-on effect. PSA Peugeot Citroen fell by 6.8%, while shares in Volkswagen dropped by 4.6%.

According to the reports, the probe centred around the plant’s engine control units, and that the investigators took personal computers of several directors.

In a statement, Renault confirmed both that its cars were involved in a French Government-led investigation to ensure that French vehicles do not contain ‘defeat devices’, and that the raid took place.

“The DGCCRF [French Agency for Energy and Climate] went to the headquarters, the Renault technical centre in Lardy and the technocentre in Guyancourt,” the statement said. “Renault’s teams are fully cooperating with the independent technical commission and the additional investigations decided by the Ministry of Economy.”

French authorities are testing 100 vehicles – including 25 Renaults, in line with its domestic market share. Four Renault models are among the first 11 vehicles tested, the results of which prompted the visit to the car maker’s facilities.

A spokesman for the company in France refused to comment any further.