WikiLeaks and its founder, Julian Assange, are facing multiple investigations by US authorities, including three congressional probes and a federal criminal inquiry, sources familiar with the investigations say.
WikiLeaks published emails hacked from the Democratic Party and the personal email account of John Podesta, Hillary Clinton's 2016 presidential campaign chairman.
In a report issued in January, the CIA, the National Security Agency, and the Federal Bureau of Investigation said Russian intelligence did the hacking, and the GRU, Russia's military intelligence agency, sent hacked data to WikiLeaks via intermediaries.
The House Intelligence Committee has questioned Roger Stone, a longtime friend of President Donald Trump and a veteran political operative who promoted WikiLeaks' disclosures of the emails on Twitter.
After initially refusing to identify an intermediary he dealt with who was in contact with Assange, Mr Stone later told the committee it was Randy Credico, a left-wing comedian.
The committee subpoenaed Credico but it is unclear whether Credico could help investigators uncover where WikiLeaks got the hacked Democratic emails.
It is not known whether Robert Mueller, the Justice Department special counsel investigating possible Russian interference in the 2016 presidential election, is investigating WikiLeaks.
A US lawyer for Mr Assange, Barry Pollack, said Mr Mueller's team had not contacted him.
Meanwhile, federal prosecutors in Alexandria, Virginia, are conducting a criminal investigation into how WikiLeaks obtained thousands of classified US government documents, including CIA materials and most recently ultra-secret technical materials describing American spy agency hacking tools. Law enforcement sources and Pollack said the probe began several years ago.
Australian-born Mr Assange has lived in the Ecuadorean Embassy in London for several years.