Evolution AB shares plunged as the Swedish online gambling giant reached out to regulators in New Jersey and launched an internal review after a competitor accused the company of doing business in banned countries.

The stock tumbled as much as 19% to 993 kronor in Stockholm, the most since its 2015 initial public offering. That extended its drop for the week to 31%, reducing the company’s market value by more than 96 billion kronor ($11 billion) to 224 billion kronor.

Chief Executive Officer Martin Carlesund said on a conference call with investors Wednesday that Evolution “pro-actively” contacted the regulators and initiated the internal review “to ensure that we can respond swiftly to any questions.”