The chips are down as Germany launches a probe into suspected potato price fixing over the past decade which may have cost consumers and farmers hundreds of millions of euros, according to local media.

The culprits face a roasting after the national competition regulator has investigated allegations that at least nine production and distribution plants illegally agreed on prices for deliveries to grocery chains as well as those paid to farmers.

The Suddeutsche Zeitung said profits peeled off by those involved in the alleged cartel -- dubbed the "Kartoffel Kartel" by the press -- could amount to hundreds of millions of euros (dollars).

Bild newspaper said investigators had raided the premises of the nine companies and that another five risked fines for links with the cartel, suggesting the illicit gains could run up to one billion euros.

But the manager of one of the businesses targeted denied there was a cartel, stating crisply: "We have absolutely no guilty conscience."