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Pentagon officials looking into the leak of thousands of classified documents to an online whistle-blower already have at least one potential suspect in mind -- an Army intelligence analyst under suspicion in an earlier leak to the same website.

Pfc. Bradley Manning was charged earlier this month with leaking classified information, presumably the 2007 video obtained by WikiLeaks.org that shows a U.S. helicopter firing on Iraqis, though Pentagon sources caution that it is too early to know whether Manning had anything to do with the latest massive leak of documents covering six years of the war in Afghanistan.

"Our first priority is to determine what damage might be done by these documents. We will attempt to determine source but we'll look broadly at potential sources, not just one individual," Pentagon spokesman Dave Lapan said. "But it is logical to assume that Pfc. Manning would be a person of interest."

Another Pentagon source told Fox News that Manning is the first person investigators will check, based on his alleged history of leaking classified video to Wikileaks, but the source insists the soldier already in custody is not the only person they'll check out.

White House Press Secretary Robert Gibbs expressed concern Monday that sensitive information is detailed in the more than 75,000 documents leaked, though he also described the contents as devoid of "broad revelations." About 15,000 more also are expected to be revealed.

Administration Calls War Document Leak Illegal, Harmful Amid Calls for Probe

The Wall Street Journal reported that military investigators are checking computers used by Manning to see if he is the source of the trove of documents released by WikiLeaks.

Pentagon spokesman Geoff Morrell told Fox News the department wants to find out who originally leaked the information to "make sure there's not any more coming." He said it remains to be seen whether any action will be taken against those involved in the leak. 

The release of the classified U.S. records on the war, marking one of the largest unauthorized disclosures in military history, cover a time period that largely predates the Obama administration as well as the new strategy and surge announced at the end of 2009. They apparently cover a period from January 2004 to December 2009. 

The documents cover much of what the public already knows about the troubled nine-year conflict: U.S. special-ops forces have targeted militants without trial, Afghans have been killed by accident and U.S. officials have been infuriated by alleged Pakistani intelligence cooperation with the very insurgent groups bent on killing Americans. 

WikiLeaks founder Julian Assange, at a news conference in London Monday, declined to comment on the identity of the source who leaked the documents, or on how the source managed to copy and leak them. Asked about Mr. Manning, Mr. Assange said: "There is no allegation as far as we can determine" that the documents posted on WikiLeaks Sunday are "connected to Bradley Manning."

He said WikiLeaks has nonetheless "committed funds" to Pfc. Manning's legal defense, offering his military-appointed legal team money in case it wants to hire civilian counsel.

Mr. Assange said the source who leaked the documents was motivated by a desire "to call attention to a number of these incidents."

Mr. Manning's military defense team didn't respond to requests seeking comment.

In early July, the U.S. military announced it would press criminal charges against 22-year-old Pfc. Manning for allegedly transferring classified military information to his computer and "delivering national defense information to an unauthorized source."

These charges appear to be connected to the leak of a classified video that WikiLeaks released to the public. The video, which depicts the July 2007 killing of two Reuters journalists and other individuals in Iraq by Apache helicopter gunships, provoked an international media sensation. In early April, Wikileaks released "Collateral Murder," a package of documents and videos related to the attack.

The organization said an anonymous leaker, credited only as "our courageous source," had furnished the materials, which included dramatic gunsight video.

According to a U.S. military charge sheet, Pfc. Manning improperly obtained secret information, including classified State Department cables and video footage of a July 2007 military operation, while stationed at a base east of Baghdad.

Fox News' Mike Emanuel, the Wall Street Journal and the Associated Press contributed to this report.