Germany's antitrust watchdog on Thursday said it had issued a 646-million euro ($720 million) fine against three steel manufacturers and three individuals for fixing prices for plate steel.

The Federal Cartel Office said Germany's Thyssenkrupp Steel Europe, Salzgitter-owned Ilsenburger Grobblech and Austria's Voestalpine Grobblech had admitted to the accusations and accepted the penalties.

At regular meetings between 2002 and 2016, representatives from the companies "agreed on the most important price supplements and surcharges for specific quarto plates in Germany," Andreas Mundt, president of the cartel office, said in a statement.

According to the competition body, the add-on prices agreed by the steel producers "accounted for around 20-25 percent of the total price of quarto plates" over the period.

Quarto plates are hot-rolled flat steel products used in shipbuilding, bridges, wind turbines and pipelines.

A fourth company, Dillinger Huettenwerke, was also involved in the cartel but escaped punishment because it was the first to cooperate with the investigation.

The steel companies accepted the penalties
The steel companies accepted the penalties AFP / PATRIK STOLLARZ

Voestalpine Grobblech likewise cooperated with Germany's Federal Cartel Office, and saw its fine reduced accordingly.

The Austrian firm separately announced it had agreed to a fine of 65.5 million euros.

"The origins of the events lie in the distant past," Voestalpine said, adding that current members of the management board "were neither involved in this matter and nor were they aware of it".

Thyssenkrupp declined to reveal the precise amount of its fine, but said it was covered by risk provisions already set aside.

In its 2018-2019 financial report, the conglomerate added another 100 million euros to previous funds set aside to cover the costs of the fine.

In a similar probe, Germany's antitrust body last month fined German carmakers BMW, Daimler and Volkswagen a total of 100 million euros for "anticompetitive practices" in buying certain steel products.