Federal prosecutors are investigating stock sales by three Equifax executives in early August, just days after the company discovered a data breach affecting the personal information of up to 143 million people.
The criminal probe, looking at whether the executives had violated insider trading laws, was reported by Bloomberg News, citing people familiar with the investigation. Equifax didn't respond to a CNBC request for comment.
Equifax says on its website that it continues to work closely with the FBI in its probe.
Shares of the credit reporting company fell 0.2 percent Monday morning. They are down nearly 35 percent in September.
Equifax's chief financial officer, the president of its U.S. Information Solutions business and the president of its Workforce Solutions division sold $1.8 million of stock on Aug. 1 and 2. A company spokesperson said the three weren't aware at the time that a security issue had been discovered by the company. The discovery was on July 29 but not announced until Sept. 7.
On Friday, Equifax said its chief information officer and its chief security officer had "retired." But the company has been scrambling to respond to the growing public outcry over the breach and how its disclosure was handled. Sen. Elizabeth Warren said she would open an investigation, and her home state of Massachusetts has said it plans to sue the company.