Prosecutors in Stuttgart said they raided German sports carmaker Porsche on Tuesday on suspicion that an auditor working for the authorities received bribes to pass information to the tax adviser of the Volkswagen subsidiary.

The investigators suspect that “an official from the Stuttgart business audit office revealed confidential information to a tax adviser of Porsche AG and accepted benefits in exchange", they said in a statement.

Almost 200 police and prosecutors searched the luxury carmaker's offices, tax collectors' offices, a tax adviser's office and private homes in and around Stuttgart for paper and digital documents.

Porsche confirmed to AFP that the searches had taken place, adding that the carmaker “is cooperating fully with the authorities".

On top of the bribery probe, investigators suspect the company made “unjustified” and "disproportionately large" payments to a former works council member.

Six people, including five from the company leadership, are alleged to have been involved in the bribery of the ex-works council member, they said. They "may have committed fraud against Porsche AG", said prosecutors.

The former works council member was not one of the people under suspicion, prosecutors said.

Tuesday's searches were not related to Porsche's role in "dieselgate", the emissions cheating scandal over which it agreed to pay a fine of 535 million euros ($669 million) earlier this month.

Its parent company Volkswagen admitted in 2015 to manipulating 11 million vehicles worldwide to appear less polluting in the lab than on the road.