Gambling regulators in 15 European jurisdictions and one US state have issued a joint statement expressing concern over increased gambling activity in video games.

On Monday, gaming regulators in Austria, the Czech Republic, France, Gibraltar, Ireland, the Isle of Man, Jersey, Latvia, Malta, the Netherlands, Norway, Poland, Portugal, Spain, the UK and the US state of Washington issued a joint letter expressing their concerns over “the blurring lines between gambling and gaming.”

The letter singles out two main areas of concern: ‘skin’ betting and loot boxes. The former involves websites that use virtual goods from eSports games as currency for gambling activities, while the latter involves the sale of virtual items hidden inside loot boxes, the contents of which aren’t revealed until after purchase, a process that critics have compared to the online slots play.

The letter also mentions social casino gaming, which mimics real-money play but involves virtual currency, as well as “the use of gambling-themed content in video games available to children.” All of the above contain what regulators describe as “similar characteristics” that prompted them to regulate online gambling in the first place.