TKAMY Thyssenkrupp AG (PK)

BERLIN—Germany's antitrust watchdog has launched a steel-price fixing investigation into six car makers, including Daimler AG, BMW AG and Volkswagen AG, and auto suppliers Robert Bosch GmbH and ZF Friedrichshafen AG.

The watchdog suspects that Germany's leading car makers and two of the world's biggest car parts suppliers agreed on prices they would pay for steel products used in car manufacturing, and comes on the heels of Volkswagen's emissions-cheating scandal, and questions about possible manipulation of diesel-engine emissions by other auto makers.

Daimler, BMW, Volkswagen, Bosch and ZF confirmed that their offices had been searched and said they were cooperating with investigators. They declined to comment further.

"We are working to clarify the situation," a spokesman for BMW said.

A spokesman for Bosch said the company would "assist the Federal Cartel Office in clarifying the matter. One of our most important principles is obeying the law."

It wasn't immediately clear which other company was being investigated.

The Federal Cartel Office provided no details about potential damages to steelmakers from the alleged price fixing. The auto industry is one of the biggest customers of Germany's steel industry, accounting for 26% of steel sales, which totaled €37.8 billion ($42.1 billion) last year, according to the German Steel Federation.

Steelmakers are under pressure from the auto industry, which has expanded the use of alternative materials to save weight. Car makers increasingly use lighter components made of aluminum or carbon fiber to help them reduce weight and meet emissions and fuel economy targets.

Germany's cartel body has the power to impose a fine equal to 10% of a company's annual revenue. The highest penalty that German antitrust authorities have ever imposed was a fine of €700 million against a group of cement companies for price fixing. The fine was later reduced to €400 million.

The Cartel Office provided few details of the investigation, but said it had sufficient cause to believe that the companies violated antitrust rules "in the area of steel purchases." Around 50 investigators searched the offices of the companies on June 23 to secure evidence.

News of the investigation appears to have caught German steelmakers by surprise.

"The allegations are fresh, the probe has just started," a spokesman for Salzgitter AG said, declining to comment on whether the steelmaker was affected.

Around 15% of the company's steel is sold to the automobile industry, and "everybody buys from everyone," he said.

Thyssenkrupp AG said it wasn't aware of whether it was affected by the allegations. The company said it would review the situation if details emerge.

A Kloecker & Co. SE spokesman declined to comment.

Ulrike Dauer and Monica Houston-Waesch contributed to this article.

Write to William Boston at william.boston@wsj.com

(END) Dow Jones Newswires

July 05, 2016 09:05 ET (13:05 GMT)

Copyright (c) 2016 Dow Jones & Company, Inc.