Story highlights David Miranda, 28, was reportedly held for nearly nine hours

He was detained under schedule 7 of the Terrorism Act 2000 in the UK

Greenwald broke the story about secret surveillance programs in the United States

The partner of Glenn Greenwald, a reporter for The Guardian newspaper who broke the story about secret surveillance programs in the United States, was held at London's Heathrow Airport on Sunday.

The detention was reported by The Guardian, which said that David Miranda, 28, was held for nearly nine hours. He was reportedly passing through the airport on his way home to Brazil after leaving Berlin.

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.

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"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.

According to The Guardian, nine hours is the maximum time allowed before authorities must either release or arrest the individual.

The newspaper reported it paid for Miranda's flights.

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.

Miranda was returning to their home in Rio de Janeiro.

"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."