A website has posted what appears to be private financial information about stars such as Jay-Z and Mel Gibson.
It has also posted information about Hillary Clinton and US vice president Joe Biden.
And Los Angeles police said they were investigating how the social security number, address and a credit report of their police chief ended up on the site.
The site also posted the same information about FBI director Robert Mueller – the bureau said it was aware of the site but declined to say whether it was investigating.
The site also targeted stars such as Beyonce, Ashton Kutcher, Kim Kardashian and Paris Hilton.
Info posted about vice president Joe Biden and former Secretary of State Hillary Clinton did not include credit reports but included addresses and other sensitive information.
Social security numbers posted on Gibson, Jay-Z and others matched records in public databases.
The site, which bears an internet suffix originally assigned to the Soviet Union, expanded throughout yesterday to add entries on Britney Spears, former vice presidential candidate Sarah Palin and others.
It did not state how the information was obtained or why the 11 people targeted on the site were selected, describing the records only as "secret files".
A Twitter profile linked to the site, and created after its existence was first reported by celebrity website TMZ, included an anti-police message in Russian. Several of the purported credit reports appear to have been generated last week.
Representatives for those targeted either declined to comment on the accuracy of the information that was posted, or they did not return messages seeking comment.
Los Angeles police chief Andrew Smith said: "The best word I can use to describe it is creepy," he said about the practice known as doxxing. "It's a creepy thing to do."