Equifax Inc, a provider of consumer credit scores, said on Thursday a hack exposed the personal details of potentially 143 million U.S. consumers between mid-May and July.

The company’s shares were down 5.4 percent in after-market trading assumably leading to further look into the matter which exposed hackers who accessed details including names, social security numbers, and, in some cases, driver’s license numbers. In addition, credit card numbers of around 209,000 U.S. consumers and certain dispute documents with personal identifying information of around 182,000 U.S. consumers were accessed, the company said. Equifax also said personal information of certain UK and Canadian residents were also hacked. The Atlanta-based company is now working with UK and Canadian regulators to investigate the breach. The company also said there was no evidence of a breach into its core consumer or commercial credit reporting databases. But if this is accurate this breach could be one of the biggest in the United States.