The Senate Finance Committee is seeking additional information from Equifax about the nature of the data breach it reported last week and the timing of insider stock sales in the days immediately after the company discovered the problem.
The breach, affecting the personal information of 143 million people, has prompted outcries on Capitol Hill and calls for hearings and additional disclosures. Already, state regulators said they would look into the matter after Equifax disclosed the issue last week.
As one of three major credit reporting companies, Equifax gathers information on hundreds of millions of Americans.
On Monday, the U.S. Senate Finance Committee, chaired by Republican Sen. Orrin Hatch of Utah, sent a letter to Equifax CEO Richard Smith asking for additional information, including whether the compromised data included records related to the Internal Revenue Service, Social Security, and Medicare and Medicaid.
"This breach will cause irreparable harm to programs within this Committee's jurisdiction by way of stolen identity, refund fraud, healthcare fraud and entitlement fraud," the letter said.
The Senate committee is also asking when the company's board and three Equifax insiders who sold $1.8 million in stock in early August were made aware of the breach, which Equifax has said it discovered on July 29.
The letter, signed by Hatch and Sen. Ron Wyden of Oregon, who is the ranking Democrat, seeks a response from Equifax by Sept. 28.
Shares of Equifax fell 8 percent on Monday after dropping 13 percent on Friday.