( CNN ) -- Glenn Greenwald , the reporter who broke the news about secret U.S. surveillance programs , said the authorities who took his partner into custody at London 's Heathrow Airport `` are going to regret what they did . '' `` I am going to write my stories a lot more aggressively now , '' the Guardian reporter told Brazil 's Globo TV on Monday in Rio de Janeiro . `` I am going to publish many more documents now . I am going to publish a lot about England , too , I have a lot of documents about the espionage system in England . Now my focus is going to be that as well . '' Greenwald 's partner , 28-year-old David Miranda , was held for nearly nine hours . He was reportedly passing through the airport on his way home to Brazil after leaving Berlin . Authorities seized his laptop , phone , and other materials . The White House knew the move was coming . `` There was a heads up that was provided by the British government , '' White House spokesman Josh Earnest said Monday . So the United States knew it `` was likely to occur , but it 's not something that we 've requested and it 's something that was done specifically by the British law enforcement officials there , '' he said . He would not comment on whether the United States has obtained material from Miranda 's laptop -- and would not say whether President Barack Obama condemns the detention . Agents asked 'about my entire life ' Miranda , also speaking to Globo TV in Rio , said agents were asking him questions `` about my entire life . '' `` I was in a room , there were six different agents coming in and out and talking to me , '' he said . `` They took my computer , video games , cell phone , everything . '' The detention was reported by The Guardian . Before releasing him , authorities seized Miranda 's laptop , cell phone , video game consoles and USB sticks , Greenwald wrote for The Guardian . `` This is obviously a rather profound escalation of their attacks on the news-gathering process and journalism , '' he said . `` It 's bad enough to prosecute and imprison sources . It 's worse still to imprison journalists who report the truth . But to start detaining the family members and loved ones of journalists is simply despotic . Even the Mafia had ethical rules against targeting the family members of people they felt threatened by . '' A Metropolitan Police spokesman confirmed that a 28-year-old man was detained Sunday at Heathrow . The spokesman said the man was held for close to nine hours under Schedule 7 of the Terrorism Act 2000 . 'Grave concern ' Brazil 's foreign ministry issued a statement Sunday expressing `` grave concern '' over the incident . Anger had erupted in Brazil when citizens learned of U.S. National Security Agency spying on Brazil . `` This measure is without justification since it involves an individual against whom there are no charges that can legitimate the use of that legislation . The Brazilian government expects that incidents such as the one that happened to the Brazilian citizen today do not repeat . '' According to The Guardian , nine hours is the maximum time allowed before authorities must either release or arrest a detained individual . Miranda was returning to their home in Rio de Janeiro . While in Berlin , Miranda stayed with filmmaker Laura Poitras , who has worked `` extensively '' with Greenwald on his stories about the National Security Agency , the reporter wrote . The Guardian reported that it paid for Miranda 's flights . `` Miranda is not a Guardian employee but often assists Greenwald in his work , '' the newspaper said . Guardian editor Alan Rusbridger , in an editorial , wrote that `` Miranda is not a journalist , but he still plays a valuable role in helping his partner do his journalistic work . '' He added that Greenwald 's work on the reams of material provided by Snowden has been `` immensely complicated by the certainty that it would be highly unadvisable for Greenwald ( or any other journalist ) to regard any electronic means of communication as safe . The Guardian 's work on the Snowden story has involved many individuals taking a huge number of flights in order to have face-to-face meetings . '' Miranda is quoted by the Guardian as saying : `` So they think I have a big connection . But I do n't have a role . I do n't look at documents . I do n't even know if it was documents that I was carrying . It could have been for the movie that Laura is working on . '' `` If the UK and U.S. governments believe that tactics like this are going to deter or intimidate us in any way from continuing to report aggressively on what these documents reveal , they are beyond deluded , '' said Greenwald . `` If anything , it will have only the opposite effect : to embolden us even further . ''
The White House knew the attack was planned , spokesman says . David Miranda , 28 , was reportedly held for nearly nine hours . Glenn Greenwald broke the story about secret spy programs in the United States . He says he 'll focus efforts on the English writing system .