WASHINGTON (Reuters) - Credit reporting agency Equifax Inc said on Tuesday it had launched an internal investigation after finding that four consumer credit reports had been fraudulently accessed.

Equifax spokesman Tim Klein said the "fraudulent and unauthorized access" was related to media reports that a website published the personal financial information of U.S. First Lady Michelle Obama, Vice President Joe Biden and celebrities including singer Beyonce and actor Ashton Kutcher.

Klein said the company's initial investigation found that the perpetrators had personal information on certain individuals, which allowed them to bypass authentication steps.

He would not name the individuals whose credit reports were involved, but said they were accessed through the www.annualcreditreport.com website.

(Reporting by Susan Heavey, Writing by Karey Van Hall; Editing by David Storey and Sandra Maler)