Renault was also investigated last year
The allegations have sent the French car maker’s share prices tumbling by 4.3%. They come a year after the car maker's headquarters were raided following earlier emissions claims.
A statement released by Renault says: "Groupe Renault acknowledges the opening of judicial investigations on the ground of "deceit on essential qualities and inspections conducted, these facts having led to the products being dangerous for the health of humans or animals".
"Groupe Renault, which intends to protect its rights, reminds its constant position: Renault complies with French and European regulations. Renault vehicles are all and have always been homologated in accordance with the laws and regulations."
"They are compliant with the applicable standards. Renault vehicles are not equipped with cheating software affecting anti-pollution systems. The States, European Commission, Regulation Authorities and automotive manufacturers all share the opinion that the requirements of the applicable regulations need to be strengthened. This is the purpose of the future Euro6d Regulation."
Yesterday, reports said Fiat Chrysler was also being investigated in the US following similar accusations regarding its own diesel units.