British investigators were granted another week to question 23 suspects in an alleged plot to blow up as many as 10 trans-Atlantic jetliners, and a Pakistan official said authorities there were seeking a British Muslim, an Eritrean and a Pakistani in connection with the case.

A suspect arrested on Tuesday was released without charge shortly after the hearing late Wednesday in London, Scotland Yard said. It did not say why, nor identify the person. Another suspect had been released without charge Aug. 11.

A Pakistani intelligence official said on Wednesday that authorities there were seeking a British Muslim of Afghan origin, an Eritrean national and a Pakistani.

The official, who spoke on condition of anonymity due to the sensitive nature of the inquiry, said the three suspects had been in contact with others who planned to blow up U.S.-bound planes leaving London. The official gave no other information about the suspects.

A district judge ruled late Wednesday that the 23 arrested since Aug. 10 and still detained can be held without charge, as investigators continued to search several homes and businesses for clues, including indications of outside help and Al Qaeda involvement.

The case is the first major test of a new terrorism law that lets suspects be held for as long as 28 days without charge while investigators try to solidify their cases.

The hearing was held behind closed doors and attended only by the suspects' lawyers, investigators and government officials.

Scotland Yard said that 21 of the suspects could be detained for questioning through Aug. 23, and two others could be detained until Aug. 21. No reason was given for the difference in the length of time.

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.

The time lets investigators examine computer hard drives and other data for clues, including whether financing for the alleged plot came from home or abroad.

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.

Home Secretary John Reid, Britain's chief law-and-order official, acknowledged that some of the suspects in the present case would likely not be charged with major criminal offenses, but said there was mounting evidence of a "substantial nature" to back the allegations.

If investigators find they need more time, they can request an extension next week.

Reid met earlier Wednesday 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 euro350,000 (US$450,000) to research the best ways to detect liquid-based explosives.

As many as 17 people have been arrested 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 transit system bombings.

The detainees in Britain and Pakistan had not attended terror-training camps in Pakistan or Afghanistan and had relied on information gleaned from text books 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.