WikiLeaks founder Julian Assange could be charged under the Espionage Act for making public classified US government documents which he obtained illegally, a media report said here today.

US authorities are investigating whether Assange, also Editor-in-Chief of the whistle-blower website, violated criminal laws by disclosing the classified information, 'The Washington Post' reported.

The FBI is examining everyone who came into possession of the documents, including those who gave the material to WikiLeaks and also the organisation itself, it said, citing those familiar with the probe.

According to the Post, charges against WikiLeaks and Assange could be filed under the Espionage Act.

"The Pentagon is leading the investigation and it remains unclear whether any additional charges would be brought in the military or civilian justice systems. Pfc. Bradley Manning, an Army intelligence analyst suspected of being the source of the WikiLeaks documents, was arrested by the military this year," the daily reported.

Under the Espionage Act, anyone who has "unauthorised possession to information relating to the national defence" and has reason to believe it could harm the United States may be prosecuted if he publishes it or "willfully" retains it when the government has demanded its return, Jeffrey H Smith, a former CIA general counsel, told the paper.

However, "no charges are imminent", sources were quoted as saying, adding it is unclear whether any will be brought.

White House Press Secretary Robert Gibbs told reporters that "the stealing of classified information and its dissemination is a crime."

"We have an active, ongoing criminal investigation with regard to this matter. We are not in a position as yet to announce the result of that investigation, but the investigation is ongoing," US Attorney General Eric Holder said.

"To the extent that we can find anybody who was involved in the breaking of American law and who has put at risk the assets and the people ..., they will be held responsible. They will be held accountable," Holder said when asked if action could be taken against Julian Assange, the WikiLeaks founder and Editor-in-Chief.