Daily fantasy sports operator DraftKings is investigating one of its player for potential complicity to win the site’s “Fantasy Football Millionaire” contest.

User Martin Crowley, who goes by the name “papagates,” was among the winners of the contest, which yielded a $1 million prize. But Crowley’s brother, Tom, also won a million dollar contest last year, which immediately resulted in speculations that the two may have colluded to win the contest.

DraftKings head of compliance Jennifer Aguiar confirmed to the Wall Street Journal that they “are in the process of on ongoing investigation.”

Aguiar declined to comment further on the specifics of the internal probe, which according to the news outlet, “appears to be focused on whether at least one winner of Sunday’s contest found ways around the site’s limits on how many entries each user can submit and the level of cooperation they can have with other players.