New findings suggest Pfc. Bradley Manning, the intelligence analyst accused of handing over the data to the WikiLeaks website, initiated the theft himself, officials said. That contrasts with the initial portrait provided by Defense Department officials of a young man taken advantage of by Mr. Assange.

Further denting the push by some government officials to prosecute Mr. Assange, the probes have found little to link the two men, though others affiliated with WikiLeaks have been tied to Pfc. Manning, officials said.

For the U.S. to bring its preferred case against Mr. Assange of inducing the leak, it would have to show that the WikiLeaks founder specifically encouraged Mr. Manning to hand over the documents, which included thousands of State Department cables, as well as low-level intelligence reports on the wars in Iraq and Afghanistan.