Stock in Evolution plunged after an anonymous competitor accused the company of accepting bets from jurisdictions where gambling is illegal, such as Hong Kong and Singapore. 

The complaint was made in a letter on Nov. 12 to the New Jersey Division of Gaming Enforcement and it also alleged the company was operating in countries subject to U.S. sanctions, Bloomberg reports. 

The news agency, which said it has seen a copy of the letter, said the complaint was filed by Ralph Marra, senior counsel at Calcagni & Kanefsky. He was retained by a U.S.-based competitor of Evolution. 

The shares tumbled 8 percent in early trading in Sweden, where the company is based. 

Carl Linton, the head of investor relations at Evolution, told Bloomberg in an email that the assertions weren’t accurate, although the company hadn’t seen the letter.

The investigators say they recorded themselves playing Evolution Games through internet addresses in Singapore and Hong Kong, where online gambling is illegal.