A criminal investigation into the leak of tens of thousands of secret Afghanistan war logs could go beyond the military, Defense Secretary Robert Gates said Thursday, and he did not rule out that WikiLeaks founder Julian Assange could be a target.
"The investigation should go wherever it needs to go," Gates said.
Gates would not be more specific, waving off questions about whether Assange, who is Australian, or media outlets that used the WikiLeaks material could be subjects of the criminal probe. But he noted that he has asked the FBI to help in the investigation "to ensure that it can go wherever it needs to go."
The Army is leading an inquiry inside the Defense Department into who downloaded some 91,000 secret documents and passed the material to WikiLeaks, an online archive that describes itself as a public service organization for whistle-blowers, journalists and activists.
The Pentagon inquiry is looking most closely at Pvt. Bradley Manning, an Army intelligence specialist who was already charged with leaking other material to the website.
The FBI would presumably handle aspects of the investigation that involve civilians outside the Defense Department, and the Justice Department could bring charges in federal court.
Investigators said they have found evidence linking Manning with the leak of secret war documents, a defense official told the Wall Street Journal on Thursday.
Officials said a search of computers used Manning showed evidence that he had downloaded the Afghanistan war logs, the Journal reported.
Earlier this month, criminal charges were filed against Manning for allegedly leaking classified video of an Apache helicopter attack in Baghdad that killed a number of civilians.
Manning faces two charges and 12 counts of illegally providing classified information to an unauthorized source.
Senior Pentagon officials told NBC News that Manning was under "suicide watch" and feared that he "may try to harm himself." He was headed back to the United States from Kuwait on Thursday, NBC News reported.
'Afghan War Diary'
Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, called the release of the documents that WikiLeaks calls its "Afghan War Diary" deeply damaging and potentially life-threatening for Afghan informants or others who have taken risks to help the U.S. and NATO war effort.
Theirs was the most sober assessment of the ramifications of the leak Sunday of raw intelligence reports and other material dating to 2004.
"Mr. Assange can say whatever he likes about the greater good he thinks he and his source are doing, but the truth is they might already have on their hands the blood of some young soldier or that of an Afghan family," Mullen said.
Assange told the Australian Broadcasting Corp. in an interview aired Thursday that WikiLeaks had contacted the White House — via The New York Times acting as intermediary — and offered to let government officials go through the documents to make sure no innocent people were identified. The White House did not respond to the approach, he said.
Assange dismissed allegations that innocent people or informants had been put in danger by the publication of the documents.
"We are yet to see clear evidence of that," he said in the Australian Broadcasting interview.
Gates said that the Pentagon is tightening rules for handling classified material in war zones as a result of the leak. He did not mention Manning by name, and Pentagon officials caution that Manning may not be the sole target of the Army inquiry.
Manning was stationed at a small post outside Baghdad. If he was the source of the Afghan war logs, he would have been amassing material he had little if any reason to see.
"If the kind of breach involved in the downloading of these thousands of documents had occurred at a rear headquarters or here in the U.S., there's a very high likelihood we would have detected it," Gates said.
The Associated Press and NBC News contributed to this report.