According to prosecutors in Bochum and the Federal Cartel Office, the antitrust case may be among the biggest in decades with 30 individuals under investigation.
Rail steel prices may have been artificially inflated by hundreds of millions of euros over the years, the Westdeutsche Allgemeine Zeitung (WAZ) reported.
The cartel allegedly operated for 10 years before breaking up in 2008. Big companies are linked to the scandal, including GfT Gleistechnik, a subsidiary of steel giant ThyssenKrupp.
"Our interest is to investigate the case quickly and comprehensively," said a company spokesman. He added that company bosses were co-operating with investigators and that the company was dedicated to doing ethical business.
According to WAZ, the members of the cartel called themselves the “rail friends” and met up to six times each year at places like Da Bruno, a Duisburg restaurant best known for a Mafia-related shooting in 2007.
To try to throw off authorities, they used code-names like “Hannibal Lecter” and “Dominatrix.”
The cartel was complex, diverse and international, prosecutors believe. It included participants from German, Swedish and Czech companies. Those involved in the scheme fine-tuned arrangements through encrypted messages and phone calls, according to WAZ.
The secret group fell apart in 2008 when a subsidiary of steel-maker ArcelorMittal undercut the cartel's prices by 35 percent, WAZ reported.