A spokeswoman for the Swedish Economic Crime Authority, which is linked to the prosecutor's office, said it was conducting a preliminary investigation of a person in the company, who it did not name.

Grinbaum's lawyer said his client denied wrongdoing. "He denies the accusations," lawyer Hans Strandberg told Reuters.

Oscar Engelbert, chief executive and main owner of Oscar Properties, said Grinbaum had been chairman since 2012. "I have never had any reason to doubt his judgement," he said in a statement.

Oscar Properties' shares closed 2.1 percent lower.

(Reporting by Olof Swahnberg; Editing by Anna Ringstrom and Adrian Croft)