It was the first major test of a new terrorism law that lets the government hold suspects for as long as 28 days without charge so investigators can solidify their cases.
The hearing, which addressed the cases of 23 suspects arrested in Britain's initial sweep last week, was held behind closed doors and attended only by the suspects' lawyers, investigators and government officials.
However, Scotland Yard said Wednesday night that a person arrested earlier this week as part of its investigation was released. In a brief statement, police said the suspect was released without charge. Scotland Yard said the suspect had been arrested on Monday.
Earlier Wednesday, Scotland Yard said that 21 of the suspects could be detained for questioning through Aug. 23, while another two could be detained until Aug. 21. No reason was given for the difference in the length of time.
The final suspect, who was arrested Tuesday, was not involved in the hearing, Scotland Yard said, adding that he remained police custody.
As CBS Radio News correspondent Charlie D'Agata reports, new anti-terror laws give the British government up to four weeks to hold suspects without charges — but lawyers must periodically appear before a judge to make the case for continued confinement.
Experts say the primary reason police could use nearly a month to complete a probe is because of the complexity of investigations into the alleged plot to smuggle liquid explosives hidden in hand luggage aboard flights.
"You've got laptops, you have to bring in translators to translate all the documents in there, and sometimes it's inopportune to release all your suspects — particularly terrorism suspects — while all that is being downloaded and translated," said Cliff Knuckey, a retired police detective who has worked on terrorism investigations.
"Terrorism investigations are different, simply because you're dealing with people who will do their best not to compromise their plans and who will do anything not to be compromised."
What the police do not want to do is bring serious charges and see them collapse, CBS News correspondent Sheila MacVicar reports. There is concern that police were pushed to disrupt the plot before they had enough firm evidence.
When police officials appeared in February before a House of Commons committee looking at Britain's terror legislation, they told lawmakers much the same thing. Deputy Assistant Commissioner Peter Clarke, who commands the anti-terrorist police branch, said officers had found terrorist training videos spliced in the middle of normal Hollywood films, meaning hours spent scrutinizing videotapes.
Previously, police were able to detain people suspected of terrorism offenses for 14 days only. But the new legislation, which became law earlier this year, also created new offenses, including preparing a terrorist act, giving or receiving terrorist training, and selling or spreading terrorist publications.
Prime Minister Tony Blair failed to receive parliamentary approval for his own plan to interrogate terrorist suspects for up to 90 days.
The British probe of a plot to destroy U.S.-bound jetliners with chemical explosions is the highest-profile case to be conducted under the new legislation.
Home Secretary John Reid, Britain's chief law-and-order official, acknowledged that some of the suspects likely would not be charged with major criminal offenses, but said there was mounting evidence of a "substantial nature" to back the allegations.
His comments came after he met with the French, German and Finnish interior ministers, Nicolas Sarkozy, Wolfgang Schaeuble and Kari Rajamaki, respectively, and EU Commission Vice President Franco Frattini. They later announced the allocation of $235,000 to research the best ways to detect liquid-based explosives.
Twenty-four suspects have been arrested in Britain in the liquid explosives plot and as many as 17 people in Pakistan, including alleged ringleader Rashid Rauf.
British national Rauf's 22-year-old brother, Tayib, is among those in British custody. Those detained in Britain whose assets were frozen range in age from 17 to 35.
Two top Pakistani intelligence agents said Wednesday that the would-be bombers wanted to carry out an al Qaeda-style attack to mark the fifth anniversary of the Sept. 11 strikes, but were too "inexperienced" to carry out the plot.
The two senior agents, who spoke on condition of anonymity, said that if the terror cell members arrested in Pakistan and Britain had appropriate weapons and explosives training, they could have emulated massive attacks like those five years ago in New York and Washington as well as the July 7, 2005, London bombings.
The detainees in Britain and Pakistan had not attended terror-training camps in Pakistan or Afghanistan and had relied on information gleaned from textbooks on how to make bombs, the officials said.
Their comments offer a different perspective from that given by U.S. Homeland Security Secretary Michael Chertoff. "Certainly in terms of the complexity, the sophistication, the international dimension and the number of people involved, this plot has the hallmarks of an al Qaeda-type plot," Chertoff said Friday.
The Pakistani officials said Rashid Rauf met with al Qaeda figures inside Pakistan before his arrest last week.
They said Rauf, a British national of Pakistani descent in his 30s, had also been in contact — through intermediaries — with the purported No. 3-ranked al Qaeda leader at large in neighboring Afghanistan. The officials declined to give the al Qaeda leader's name.
Meanwhile, air service nudged closer to normal at major London airports, but British Airways said it canceled 35 flights from Heathrow Airport and another 11 at Gatwick.
There was new concern about security after a 12-year-old boy managed to board a plane at Gatwick on Monday without a passport, ticket or boarding pass. He was detected by cabin crew and removed before the flight took off. Authorities said he went through a full security screening before boarding the flight and he didn't pose a threat at any time.