Shares in online gambling company 888 Holdings have fallen by 8% after it revealed it was under investigation by the UK Gambling Commission (UKGC).
The firm said the UKGC was assessing "certain measures" taken by 888's UK subsidiary to ensure "social responsibility to its customers".
The review will examine the effectiveness of the ways customers can ask to be excluded from gambling.
The company said it would work with the UKGC on the review.
888 said the review would assess "effective self-exclusion tools across different operating platforms".
The company's UK business, which accounts for about 45% of group revenues, is involved in poker, casino, sports and bingo gambling.