FILE PHOTO: Credit reporting company Equifax Inc. corporate offices are pictured in Atlanta, Georgia, U.S., September 8, 2017. REUTERS/Tami Chappell/File Photo

(Reuters) - U.S. credit reporting firm Equifax Inc EFX.N said about 2.5 million additional U.S. consumers may have been impacted by a cyber attack at the company last month.

Equifax disclosed last month that personal details of up to 143 million U.S. consumers were accessed by hackers between mid-May and July, in one of the largest data breaches in the United States.

Cybersecurity firm Mandiant, which did the forensic review, also concluded that there was no evidence the attackers had accessed databases located outside of the United States, Equifax said in a statement.