At least one of the suspects questioned over the alleged plot to blow up transatlantic aircraft is being investigated for links to the 9/11 attacks on America.

They may have contacted Said Bahaji, wanted for helping to organise the attacks on New York and Washington in 2001, according to reports.

The computer expert shared a flat in Hamburg with Mohamed Atta, the lead hijacker of the two planes that smashed into the World Trade Centre.

He left Germany for Pakistan a week before September 11, 2001, and has been on the run ever since.

"There have been some contacts but we don't know for sure how concrete they have been," the German interior minister Wolfgang Schauble confirmed in a television interview with ZDF.

"It would have been surprising if there wasn't any contacts to Germany considering the international network of terrorism."

Unconfirmed reports said one or two of the British suspects may have been in touch with Bahaji through his wife, Nese, who still lives in Hamburg.

50 people held worldwide

British police are still questioning 23 people over the alleged plot to detonate liquid explosives mid-flight on up to ten US-bound airliners.

On Monday, police was granted permission to quiz the 23rd suspect until Wednesday, when a district judge will decide if any of them could be held longer.

In Pakistan, more arrests over the last two days brought their total number in custody to at least 17.

Officials in the Middle-Eastern country earlier said the detainees, held over the alleged plan plot, include the "key" suspect Rashid Rauf.

Rauf's brother Tayib, 22, was arrested in Birmingham and is on a list of 19 terror suspects whose assets were frozen under an order from the Treasury.

The new arrests in Pakistan mean as many as 50 people worldwide could have been involved in what police chiefs have called a plan to "commit mass murder on an unimaginable scale".

Charity money

In another sign of the investigation's global scale, the New York Times reported that money raised in Britain to help victims of the earthquake in Kashmir may have gone to the suspected plotters in Pakistan.

The money went to Jamaat ud Dawat (JuD), the charitable arm of the extremist group Lashkar-i-Taiba, which was banned by the Pakistani government after pressure from America.

Although the charity is not registered in Britain, thousands have been donated to it in mosques across London, Birmingham and Manchester.

JuDdenied that it used the money to fund the alleged plot. "We have nothing to do with this alleged plot and have no link to this," its representive Yahya Mujahid told reporters.

Attack 'highly likely'

Back home searches continue in woods in High Wycombe, Bucks, while the threat level has been lowered to its second highest from "critical" to "severe". It means a terror attack is no longer "imminent", but still "highly likely", according to MI5.

From Tuesday, hand luggage restrictions have been eased accordingly. Where all but the barest essentials have been banned the last five days, passengers can now carry a single case the size of a small laptop bag on board.

Delays due to the tight security caused at least 130 flight cancellations at Heathrow, Gatwick and Stansted airports yesterday. Although delays will continue, they were expected to ease up this week.

On Monday, the Met police chief Sir Ian Blair explained why police decided to swoop last Thursday.

"We have been behind this group of people for some time," the commissioner said. "What we always have to do is balance waiting to gather more evidence and make sure you get all the people, against the risk to the public by not moving in earlier.

"That's the decision that was reached last Wednesday evening. There's a point where the information reaches a level of concern that means if you don't take action it is indefensible."