Britons Question Whether Detention of Reporter’s Partner Was Terror-Related

Marcelo Piu/European Pressphoto Agency

David Michael Miranda, left, with his partner, Glenn Greenwald. Mr. Miranda was held Sunday for nine hours in London.

LONDON â€" Demands grew on Monday for the British government to explain why it had used antiterrorism powers to detain the partner of a journalist who has written about surveillance programs based on leaks by the former National Security Agency contractor Edward J. Snowden.

David Michael Miranda spoke to reporters at Rio de Janeiro's International Airport on Monday.

David Michael Miranda, a Brazilian citizen and the partner of the American journalist Glenn Greenwald, who lives in Brazil, was held Sunday at London’s Heathrow Airport for nine hours, the maximum allowed by law, before being released without charge. He said Monday that all of his electronic equipment, including his laptop computer and cellphone, had been confiscated.

Mr. Miranda was traveling from Berlin to Rio de Janeiro. In Berlin, he had met with Laura Poitras, an American filmmaker who has worked with Mr. Greenwald on the Snowden leaks about secret American and British surveillance programs that they argue violate individual rights and liberties.

The Guardian newspaper, where Mr. Greenwald is a columnist, reported that it had paid for Mr. Miranda’s flights but that he was not an employee of the paper. “As Glenn Greenwald’s partner, he often assists him in his work,” The Guardian said in statement. “We would normally reimburse the expenses of someone aiding a reporter in such circumstances.”

In an e-mail Monday to The Associated Press, Mr. Greenwald said that he needed material from Ms. Poitras for articles he was working on related to the N.S.A., and that he had things she needed. “David, since he was in Berlin, helped with that exchange,” Mr. Greenwald wrote.

Keith Vaz, an opposition Labor Party legislator who is chairman of Parliament’s Home Affairs select committee, said he had written to the head of London’s Metropolitan Police Service, which has jurisdiction in the matter, to ask for clarification of what he called an extraordinary case.

“What needs to happen pretty rapidly is, we need to establish the full facts,” he told the BBC. “Now you have a complaint from Mr. Greenwald and the Brazilian government â€" they indeed have said they are concerned at the use of terrorism legislation for something that does not appear to relate to terrorism. So it needs to be clarified, and clarified quickly.”

The editor of The Guardian, Alan Rusbridger, disclosed on Monday that the British government had sent officials from Government Communications Headquarters, which is known as GCHQ and is the British version of the National Security Agency, to the newspaper’s offices in London to destroy computers containing documents leaked by Mr. Snowden. Mr. Rusbridger said that he had protested that the same information was available elsewhere, but that the officials had insisted on proceeding.

“And so one of the more bizarre moments in The Guardian’s long history occurred â€" with two GCHQ security experts overseeing the destruction of hard drives in The Guardian’s basement just to make sure there was nothing in the mangled bits of metal which could possibly be of any interest to passing Chinese agents,” he wrote, adding, “We will continue to do patient, painstaking reporting on the Snowden documents, we just won’t do it in London.”

The police said in a statement that Mr. Miranda, 28, had been lawfully detained under Schedule 7 of Britain’s Terrorism Act 2000, which allows them to stop and question people traveling through ports and airports to determine whether they are involved in planning terrorist acts.

Mr. Vaz and his party said they wanted to know how the government could justify using Schedule 7 in this case, arguing that any suggestion that antiterrorism powers had been misused could undermine public support for those powers.

A Home Office spokesman said Monday that the detention was an operational police matter and that neither he nor the police would provide any details. “Schedule 7 forms an essential part of the U.K.’s security arrangements,” the spokesman said. “It is for the police to decide when it is necessary and proportionate to use these powers.”

Charlie Savage contributed reporting from Washington.

A version of this article appears in print on August 20, 2013, on page A6 of the New York edition with the headline: Britons Question Whether Detention of Reporter’s Partner Was Terror-Related.