IOWA CITY, Iowa (AP) — A U.S. Senate oversight committee is demanding information about how state lotteries are increasing security after an insider allegedly rigged jackpots for years.

Sen. John Thune, chairman of the Committee on Commerce, Science and Transportation, says fraud allegations in lottery games raise serious concerns. Yet he says it’s not clear what the Multi-State Lottery Association is doing to address them.

In a letter to association leaders obtained by The Associated Press, Thune says his committee wants answers to several questions by July 7.

Investigators say the association’s former security director, Eddie Tipton, installed software code that allowed him to predict winning numbers on specific days of the year. A jury has convicted Tipton of rigging a $16.5 million jackpot, and he’s charged with manipulating games in four other states.