Police probing an alleged airline bomb plot are continuing to search more than 20 properties, while they also question 23 suspects.
Police have been given extra time to question 23 suspects
A judge granted Scotland Yard anti-terror officers an extra seven days to question 21 suspects, and an extra five days to question two.
A person arrested on Tuesday has been released without charge.
Meanwhile, officers are said to have discovered "items of interest" in woods near some suspects' addresses.
The BBC has learnt that officers made the discovery during their search of a piece of woodland called King's Wood in High Wycombe
ARRESTS OVER 'BOMB PLOT'
10 August: 24 people arrested in London, High Wycombe in Buckinghamshire, and Birmingham
11 August: One released by police without charge
15 August: Another person arrested in Thames Valley area
16 August: Police given extra time to question suspects; one person held in Thames Valley area released without charge
21 August: Police have until this date to question two of the suspects arrested on 10 August
23 August: Police have until this date to question 21 of the suspects arrested on 10 August
It is thought they were looking for explosive detonators about the size of cigarettes.
Meanwhile, a woman who sparked an alert on a flight from Heathrow to Washington DC on Wednesday was reportedly suffering from claustrophobia.
The woman was detained by police after causing a major security alert when she became unruly after a panic attack, and was found to be carrying hand cream and matches.
The jet escorted by two F15 fighter jets.
In other developments:
- Major hospitals around the UK are ill-prepared to cope with a major incident, a survey of doctors has warned
- A public meeting is to be held in Walthamstow, east London, on Thursday evening to discuss the arrests - several of which were made in the area
- Flights are gradually returning to normal, with British Airways saying it has no plans to cancel any long-haul flights on Thursday
- BA also said it hoped to return the 5,000 pieces of luggage misplaced in the confusion at Heathrow by the end of Thursday
The 23 suspects in custody in London were arrested in raids in London, High Wycombe in Buckinghamshire, and Birmingham last week.
Under the 2006 Terrorism Act the maximum period someone suspected of terrorist activity can be held without charge is 28 days, subject to regular court approval.
It is believed up to 17 people are being held in Pakistan over the alleged plot - with two British nationals of Pakistani descent among them.
Pakistani officials said one of the Britons, Rashid Rauf, was believed to have links to al-Qaeda, but they released no details about the other Briton.
Mr Rauf is believed to have played a pivotal role in planning the operation, as well as being the go-between between al-Qaeda and the alleged plotters in Britain.
According to the Associated Press new agency, Pakistani officials believe he was the planner of the alleged attacks and recruited people to take part.
"We have reason to believe that it was al-Qaeda-sanctioned and was probably cleared by al-Zawahri [al-Qaeda's second in command]," an intelligence source was quoted as saying.