The Nevada Gaming Control Board has said unlicensed daily fantasy sports inside the state must cease and desist as of Thursday, according to media reports. In a notice to licensees, the board stated that daily fantasy sports (DFS) meets the definition of a game or gambling game.

"Moreover, because DFS involves wagering on the collective performance of individuals participating in sporting events, under current law, regulation and approvals, in order to lawfully expose DFS for play within the State of Nevada, a person must possess a license to operate a sports pool issued by the Nevada Gaming Commission," according to a statement.

The announcement comes one day after reports emerged that the Department of Justice and the FBI have launched an investigation into the legality of daily sports operators. FBI agents from the Boston office had reportedly started contacting customers of DraftKings, asking them about their interactions with the company, the Wall Street Journal reported Wednesday.

The investigators were reportedly trying to determine whether daily fantasy sports games are a form of gambling. But DFS operators, such as DraftKings and FanDuel, have insisted they offer a game of skill, which makes it legal under terms of the Unlawful Internet Gambling Enforcement Act of 2006. The act prohibits financial companies from transferring money to online gambling sites, but games of skill are exempt.