A suitcase full of bomb making material has been found by police searching woods near High Wycombe in connection with the alleged aircraft bomb plot, it has been reported.
The case contained "everything you would need to make an improvised device", unnamed police sources have told The Times and the BBC.
Scotland Yard would not officially confirm the find in the Buckinghamshire area known as King's Wood.
The material in the case could include liquids or gels that could be mixed to make explosives, simple detonators and methods to disguise it all.
It is thought the suspected plotters aimed to hide the liquids in ordinary drink bottles and the detonators in electronic gadgets like MP3 players.
Meanwhile, a young father from Micklefield stumbled across what he claims to be a terrorist hideout in the same woods.
Roy Wingrove, 23, and his younger brother Mark, 22, from Buckingham Drive, High Wycombe, were creeping around King's Wood with a camera on Sunday trying to take photographs of the police investigation to sell to the media.
Mr Wingrove said: "There was a hut with clear plastic sheeting on the sides and leaves camouflaging the top.
"Right next to it there were lots of books on Islam and paperwork. One of the books was called Islam Around the World. They were burnt and sitting in a pile."
Roy led the police to the hut, near a pond, which he says has since been cordoned off.
He says the hut was around 6ft long and 5.5ft tall and he claims to have taken photographs of the hut and evidence bags.
The Met has not confirmed the find.
On Monday, officers were photographed carrying black bags full of unidentified material from the woods in Totteridge, close to where at least four suspected plotters were arrested last week. Again police would not comment on the contents.
49 searches
A total of 49 homes and businesses have been searched since last Thursday's raids uncovered the alleged plot to blow up transatlantic aircraft in mid-air.
Thirty-six searches have been completed while 14 are still ongoing - including the one in the woods, a Scotland Yard spokesman said.
On Wednesday police were granted extra time to question 23 suspects arrested last week across London, High Wycombe and Buckinghamshire.
At Heathrow airport, all flights have returned back to normal the past week's travel chaos caused by draconian security checks.
British Airways cancelled 19 flights on Thursday, bringing its total cancellations since last Thursday to almost 1,300 - more than 1,000 of which at Heathrow.
The airline said it had managed to reunite most of the 5,000 pieces of luggage mislaid in the chaos with their owners.
Although restrictions have now eased from the initial blanket ban on cabin bags, the situation has not returned to how it was before. Each passenger can only carry one case on board, about the size of a small laptop bag.
Far from normal
But in the quiet High Wycombe neighbourhood that suddenly became an anti-terrorism crime scene, life is still far from normal. Residents have been worried after seeing television reports that claimed detonators had been found in the woods earlier this week.
The lack of information about police operations in the town has caused anxiety in the community but six police on horses have been drafted in to reassure the public.
One of the riders, PC Tim Pollock, said: "Not a lot of people want to go up and speak to a policeman but the horse can break down the barriers."
Oscar Howlett, 55, of Micklefield Road, said he felt reassured walking his dog Taz, a ten-year-old Staffordshire Bull Terrier, through King's Wood twice a day.
Mr Howlett said: "I haven't got a clue what they are doing in there but it must be important to need so many people. Micklefield is probably quite safe at the moment with all these policemen around, at least we know nothing bad is likely to happen here now."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article