Social Security numbers posted on Jay-Z, Gibson and others matched records in public databases.
The site, which bears an Internet suffix originally assigned to the Soviet Union, expanded throughout the day Monday to add entries on Britney Spears, former vice presidential candidate Sarah Palin, and others.
The site did not state how the information was obtained or why the 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.
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Representatives of 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 Cmdr. Andrew Smith said the LAPD was investigating the posting of Beck's information and would also investigate the posting of info on any celebrities who live in the city and request an inquiry.
He said confidential information on top police officials has been posted online at least twice before.
"People get mad at us, go on the Internet and try to find information about us, and post it all on one site," 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."
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Frank Preciado, assistant officer in charge at the LAPD online section, said the postings are also illegal. He said the information was likely taken from what is supposed to be a secure database of city employees.
Several of the pages featured unflattering pictures of the celebrities or government officials whose information was posted.
The site's page on Beck includes a taunting reference to former officer Christopher Dorner, who apparently committed suicide after he killed four people during a multi-day rampage. Beck's page included the message "(hash)YouCantCornerTheDorner" and an image of a woman protesting police corruption.
While government officials often have to disclose details on their finances — and celebrity divorces sometimes feature public financial data — the information posted online exceeds those disclosures.
Social Security numbers are rarely included in public records anymore because they can be used for identity theft.