The New York Times reports:

Prosecutors investigating the disclosure of thousands of classified government documents by the anti-secrecy group WikiLeaks have gone to court to demand the Twitter account activity of several people linked to the organization, including its founder, Julian Assange, according to the group and a copy of a subpoena made public late Friday.

The subpoena is the first public evidence of a criminal investigation, announced last month by Attorney General Eric H. Holder Jr., that has been urged on by members of Congress of both parties but is fraught with legal and political difficulties for the Obama administration. It was denounced by WikiLeaks, which has so far made public only about 1 percent of the quarter-million confidential diplomatic cables in its possession but has threatened to post them all on the Web if criminal charges are brought.

Dozens of Pentagon and State Department officials have worked for months to assess the damage done to American diplomatic and military operations by the disclosures. In recent weeks, Justice Department officials have been seeking a legal rationale for charging Mr. Assange with criminal behavior, including whether he had solicited leaks.

The move to get the information from five prominent figures tied to the group was revealed late Friday, when Birgitta Jonsdottir, a former WikiLeaks activist who is also a member of Iceland’s Parliament, received an e-mail notification from Twitter.

In the message, obtained by The New York Times, the company told her it had received a legal request for details regarding her account and warned that the company would have to respond unless the matter was resolved or “a motion to quash the legal process has been filed.” The subpoena was attached.

The subpoena was issued by the United States attorney for the Eastern District of Virginia on Dec. 14 and asks for the complete account information of Pfc. Bradley Manning, the Army intelligence specialist awaiting a court martial under suspicion of leaking materials to WikiLeaks, as well as Ms. Jonsdottir, Mr. Assange and two computer programmers, Rop Gonggrijp and Jacob Appelbaum. The request covers addresses, screen names, telephone numbers and credit card and bank account numbers, but does not ask for the content of private messages sent using Twitter.

Some published reports in recent weeks have suggested that the Justice Department may have secretly impaneled a grand jury in the Eastern District of Virginia, which often handles national security cases, to take evidence in the WikiLeaks inquiry. But the subpoena, unsealed by a Jan. 5 court order at the request of Twitter’s lawyers, was not issued by a grand jury.

In Twitter messages, WikiLeaks confirmed the subpoena and suggested that Google and Facebook might also have been issued such legal demands. Officials for Facebook declined to comment, and Google did not immediately respond to an inquiry.

Meanwhile, WikiLeaks tweeted: “WARNING all 637,000 @wikileaks followers are a target of US gov subpoena against Twitter, under section 2. B http://is.gd/koZIA”

I’m not going to hold my breath waiting for an email notification from Twitter. As for the silence from Google and Facebook — that speaks volumes.