Equifax (EFX) said Thursday that hackers have gained access to personal information belonging to 143 million U.S. consumers after exploiting a vulnerability on the credit bureau's website.

The hack occurred between mid-May and July, according to Equifax, one of the nation's biggest credit reporting agencies. The leaked information includes names, Social Security numbers, birth dates and in some cases driver's license numbers.  

Credit card numbers for about 209,000 consumers and documents related to credit reporting disputes for 182,000 people also were exposed.

Equifax said hackers also accessed some information from British and Canadian consumers. The company doesn't think residents of other countries were affected.

Equifax has found no evidence of unauthorized activity on the company's core consumer or commercial credit reporting databases. It discovered the intrusion on July 29 and acted immediately to stop it, the company said. 

Equifax also said it has alerted law enforcement about the cyberattack.

Personal finance experts warned consumers who may have been affected by the hack to be on their guard.

"When breaches like these happen, consumers need to be diligent -- and not just in the short term," said Matt Schulz, senior industry analyst with CreditCards.com. "Just because nothing looks amiss on your bank statements or your credit report now, that doesn't mean you haven't been compromised. Bad guys can be very patient, so it's important to keep an eye out long after this story fades from the headlines."

This is a developing story