WASHINGTON – The FBI is investigating whether the financial records and other personal information of leading political figures, including Vice President Biden and first lady Michelle Obama, may have been illicitly accessed and published online, according to Justice Department officials.

A website posted what appear to be credit reports, banking information, Social Security numbers and addresses for several officials, as well as a number of celebrities. In addition to Biden and Obama, the site purported to have obtained records of Attorney General Eric Holder Jr., former secretary of state Hillary Rodham Clinton and FBI Director Robert Mueller III.

The website used the Internet suffix .su, which suggested that it was based in Russia or a post-Soviet republic.

It was unclear how the documents, if confirmed as authentic, could have been obtained. A Justice Department official, speaking on the condition of anonymity because the investigation is ongoing, said the FBI is trying to determine whether it might be a case of identity theft, hacking or perhaps both.

The White House declined to comment.

Much of the posted material was drawn from credit reports from organizations such as TransUnion and Equifax. Tim Klein, a spokesman for the credit-reporting agency Equifax, said the company was investigating “fraudulent and unauthorized access” to four consumer credit reports and is working closely with law enforcement officials.

“Nothing is more important to us than data security, and we have stringent measures in place for protecting the data entrusted to us,” Equifax said in a statement. “We enable consumers to access their credit reports through a variety of channels, including annualcreditreport.com, which is a free service. In order for a consumer to have access to their credit report through this channel, they must provide Personally Identifiable Information that should be known only to the individual.”To obtain free credit reports, consumers are typically required to answer about five to seven questions that detail information such as the applicant’s monthly mortgage payment, who holds their car loan or the last payment amount on a particular credit card. It is not known how that kind of information was obtained about those whose credit reports were posted.

The website that posted the purported records also disclosed what it claims were the records of celebrities including Kim Kardashian, Ashton Kutcher, Arnold Schwarzenegger, Beyonce and Jay-Z.