A payment processing company that handles a significant number of transactions for the two dominant daily fantasy sports companies notified the operators this week that it would no longer handle their payments and in fact was leaving the industry altogether. It is perhaps the biggest blow yet to an industry that has been pummeled by legal challenges in recent months.

Vantiv Entertainment Solutions, the processing company, told its daily fantasy clients, which include FanDuel and DraftKings, that it would “suspend all processing for payment transactions” related to daily fantasy sports in the United States and its territories on Feb. 29.

The company cited the unfavorable opinions that have been issued by state attorneys general in recent months. Seven states, including Mississippi on Friday, have concluded that daily fantasy games were a form of gambling or were illegal under their current laws.

“As you are aware, an increasing number of state attorneys general have determined that daily fantasy sports (‘D.F.S.’) constitute illegal gambling,” Jonathan Ellman, chief transaction and marketing counsel at Vantiv, wrote in a letter obtained by The New York Times. “Although in recent weeks D.F.S. operators have raised numerous arguments to the contrary, to date those arguments have been unsuccessful and/or rejected.”