The New York state attorney general on Tuesday ordered the fantasy sports sites DraftKings and FanDuel to stop accepting bets in New York, saying the operations are essentially illegal gambling, according to copies of letters to the companies seen by Reuters.

DraftKings and FanDuel have been at the center of a firestorm of controversy since a DraftKings employee won $350,000 from a $25 entry in an American football contest on the rival FanDuel site in early October. The two companies then banned their employees from playing, but local and federal authorities began to investigate whether the fantasy sites offer games of chance, which are essentially gambling.

The letters on Tuesday from the office of New York Attorney General Eric Schneiderman said that the fantasy sites are considered gambling because customers "are clearly placing bets on events outside of their control or influence, specifically on the real-game performance of professional athletes."