LONDON – Disquiet continued to grow Tuesday over the detention of Guardian journalist Glen Greenwald’s partner, David Miranda, who was held for nine hours at London’s Heathrow Airport on Sunday.

Miranda was ferrying material related to the Edward Snowden story between filmmaker Laura Poitras in Germany and Brazil, where Greenwald is based.

Snowden’s leaks have served as the jumping off point for a series of stories about America’s globe-spanning surveillance program, including revelations that U.S. spies reach deep inside private companies to keep track of tens of millions of innocent Americans’ phone and Internet conversations with limited independent oversight. The stories have emboldened privacy activists and embarrassed President Obama, who recently unveiled a slate of intelligence reforms intended to calm public concerns.

LEGALITY QUESTIONED

Legal commentators have questioned the legality of Miranda’s detention, which civil liberties groups have decried as an abuse of power aimed at sabotaging Greenwald’s coverage.

The British government has declined to comment on the shattered hard drives, but it defended its decision to detain Miranda, saying it was right to stop anyone suspected of possessing “highly sensitive stolen information that would help terrorism.”

A law firm representing Miranda has begun legal action against the government, calling his detention unlawful and seeking assurances that British officials would not share the material seized from Miranda with anyone else. In a letter released to The Associated Press, London-based Bindmans called on the government to return a “mobile phone, laptop, memory sticks, smart-watch, DVDs and games consoles” taken from Miranda.

“These items contain sensitive, confidential journalistic material and should not have been seized.”

Experts have suggested the government’s case is dicey. The piece of legislation used to stop Miranda — Schedule 7 of the 2000 Terrorism Act — is especially contentious because it allows police to stop people for passing through airports for up to nine hours without suspicion they have committed an offense.

LOOKING FOR TERRORISTS

British legal blogger David Allen Green said Schedule 7 could only be used to determine whether or not a person was a terrorist — and not, as he put it, “a fishing expedition for property.”

“If the questioning, detention, and search of Miranda was for a purpose other than to determine if he was a terrorist, then it was unlawful,” he said.

David Lowe, a former police officer and academic at Liverpool John Moores University, said in a telephone interview that he believed the government was acting in good faith, although he said he could understand why journalists might be concerned.

He argued that the Snowden leaks could contain details of intelligence operations against groups such as al-Qaida, which he said was where anti-terror laws could come into play.

“It’s a thin connection,” he acknowledged.

British Home Secretary Theresa May took that line of argument in her comments Tuesday.

“I think it’s absolutely right that if the police believe that if somebody is in possession of highly sensitive stolen information that could help terrorists, that could risk lives or lead to a potential loss of life, that the police are able to act, and that’s what the law enables them to do,” May said.