Journalist Glenn Greenwald of the The Guardian has been publishing information leaked by Snowden, a former U.S. National Security Agency contractor now in Russia under temporary asylum.
Greenwald's partner, David Michael Miranda, 28, was detained for nine hours while on a stopover at London's Heathrow Airport on trip from Germany to Brazil, where Miranda and Greenwald live, The New York Times reported.
Miranda had been visiting Laura Poitras, a documentary filmmaker who also helped to air Snowden's leaks, in Berlin. The Times said Miranda's trip had been paid for by The Guardian.
Miranda was told he was being held under Section 7 of the British Terrorism Act, Greenwald told the newspaper Sunday The act allows someone to be held up to nine hours for questioning to determine possible ties to terrorism.
London's Metropolitan Police Service had jurisdiction in the case, and said Miranda had been lawfully detained under the Terrorism Act and released. The police statement gave no details.