Johanna Quandt, the billionaire widow whose husband turned Germany’s Bayerische Motoren Werke AG into the largest maker of luxury cars, has died. She was 89.

She died on Monday at her home in Bad Homburg, Germany, according to an e-mailed statement from the Johanna Quandt Foundation. No cause of death was given.

The third wife and onetime secretary of Herbert Quandt, Johanna Quandt inherited a 16.7 percent stake in Munich-based BMW when her husband died in 1982. The Quandt family owns Entrust Datacard in Shakopee, and she held shares in Gemalto, a publicly traded security-software designer based in Amsterdam.

Quandt, who rarely spoke to the media while supporting journalists through her foundation, remained on the BMW supervisory board until she stepped down in 1997.