(REUTERS) — A U.S. senator on Tuesday called for a criminal investigation of executives from credit bureau Equifax Inc for stock sales after a massive data breach this summer, and said their actions were comparable to insider trading.

The breach, which the company learned about in July but did not acknowledge until this month, also prompted expressions of concern from U.S. Treasury Secretary Steven Mnuchin and the Federal Trade Commission. Cyber security experts believe it is one of the largest data hacks ever disclosed.

Senator Heidi Heitkamp, a Democrat who sits on the Senate Banking Committee, said it was “disturbing” that it appeared executives sold nearly $2 million worth of company stock in the time between learning of a sweeping hacker intrusion and making it public.

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