French carmaker Renault saw its shares plunge over 20%, the biggest decline since August, after reports that fraud investigators had seized company computers as part of an alleged probe into emissions testing.

Agents from the economy ministry's fraud office inspected a number of Renault sites related to engine certification and standards testing on 7 January, according to local unions, although both the car manufacturer and the French authorities have declined to comment.

Earlier on 14 January, citing a flier published by the CGT union representing workers at the company's site in the French town of Lardy, AFP reported the developments, which had an immediate impact on the company's share price.

At 10.50am CET (9.50am GMT), Renault shares had fallen 8.3% to €79.51 (£60.33, $86.81) , at the time the biggest intraday decline since 24 August.

If confirmed, the investigation could be related to the Volkswagen emission scandal.