Equifax has revealed 2.5 million more Americans than previously thought may have had information compromised in a huge cyber Security Breach at the firm.
The update came a day before former boss Richard Smith testifies in Congress about the attack.
Mr Smith apologised ahead of the hearing for the firm's failings.
Critics say the company failed to take proper steps to guard information - such as Social Security numbers, birth dates and addresses - and waited too long to inform the public.
Equifax disclosed the attack last month, estimating that about 400,000 Britons and 100,000 Canadians may also have had data compromised.
On Monday, the firm raised its estimate for US customers, but lowered it to only 8,000 Canadians after further investigation.