Police hunting the men behind the 21 July bomb attacks on London have seized a car and are continuing to search a block of flats for evidence.
The car seized in north London has been taken away for examination
Security sources say one of the bombers may have used the white VW Golf, seized in East Finchley, north London.
Officers searching the block where bomb suspect Yasin Hassan Omar lived in New Southgate found what sources called large amounts of "possible explosives".
Five people have so far been arrested in connection with the failed bombings.
None of the five, all held under anti-terror laws, is thought to have been among the bombers.
Earlier, police sealed off part of the A406 North Circular road and the A1000 Finchley High Road while they examined the car.
It was checked for explosives and the security cordon lifted once police knew it was safe.
The vehicle, described as "scruffy", was thought to have been abandoned about a month ago. Officers later removed it from the scene in a covered truck.
Police are hunting for Muktar Said Ibrahim (L) and Yasin Hassan Omar
Eyewitness Andrew Lim told BBC News police had cordoned off the road at about 1030 BST.
He described seeing scores of police officers descend on the scene, along with fire engines and ambulances, while helicopters circled overhead.
About 100 people were evacuated from nearby homes.
Meanwhile, the family of Muktar Said Ibrahim, 27 - also known as Muktar Mohammed Said - who police believe was the Number 26 bus bomber, have said they knew nothing about his involvement until they saw his picture on the news.
In a statement, they said they were "shocked" when they saw it and immediately contacted police.
The family's home in Stanmore, north east London, is being guarded by police.
A flat linked to one of the bomb suspects is being examined
Police remain at the 12-storey Curtis House, in Ladderswood Way, New Southgate, which was stormed by armed officers on Monday.
Counter-terrorism sources confirmed a "large amount" of "possibly" explosive material had been found there.
Speaking on the Channel 4 news, Met chief Sir Ian Blair said: "I can say that the finds are significant.
"It's also fair to say that the speeds in this investigation is astonishing. I think my men and women are doing an extraordinary job."
Police believe an underground car park attached to the flats could have been used to store bomb-making materials.
Materials which could have been used for bombs have been discovered in rubbish chutes and bins inside the building.
HELP FOR 7 JULY BOMB VICTIMS
Helpline: 0845 054 7444 (open 24 hours)
Help centre: Lindley Hall (Royal Horticultural Halls and Centre) 80 Vincent Square, London, SW1P 2PE (open 0800 BST to 2200 BST daily)
Detectives are also investigating the possibility some of the bombers may have returned to Curtis House after Thursday's failed attack.
Neighbour Tanya Wright, who lives on the floor below Omar's flat, told BBC News she saw at least one of the suspects there in a group on Friday.
She said: "As soon as they saw me and the dog they looked very suspicious and very worried and just saw me and panicked and jumped back into the flat and slammed the door."
Detectives have no evidence the suspects have left the country and believe they may be hiding in a safe house in the capital.
London mayor Ken Livingstone told BBC News: "There's a very real risk they will have gone straight to a safe house and be just locked into it, perhaps with a lot of supplies there."
He asked anyone who had noticed suspicious "comings and goings" at a house near them to come forward.
BBC home affairs correspondent Margaret Gilmore said police were "optimistic" they would catch the bombers.
She said: "They're still hoping these men will break cover, someone will spot them, it will be a member of the public that phones in and that is how they'll catch them."
Police have linked Omar to the attack on a Victoria line Tube train between Warren Street and Oxford Circus on 21 July.
Enfield Council confirmed he had been a tenant at Curtis House, where he received £75 a week in housing benefit.
Ibrahim has been linked to the same address.
Both men have been legally resident in the UK for more than 10 years, having arrived as child dependents of asylum seekers, the Home Office says.
Omar, 24, is a Somali who arrived in Britain aged 11 in 1992 and was granted indefinite leave to remain in May 2000.
Ibrahim is a naturalised British citizen who arrived from Eritrea in 1992, aged 14. He was issued with his British passport in September 2004.
According to Harrow Borough Council, someone called Muktar Mohammed Said attended Canons High School in Stanmore, between 1991 and 1994.
Police believe this man tried to bomb a Tube at Oval station
Two other men are being sought in connection with failed bombings - one near Shepherd's Bush, west London, the other near Oval station, south London.
There are also fears a fifth bomber is on the loose after a device was found in Little Wormwood Scrubs, west London, on Saturday.
Margaret Gilmore says police have a "good idea" who the remaining bombers are.
Police have been given extra time to question a man arrested in Tulse Hill, south London, on 23 July.
He can now be held until 27 July, along with two men arrested in Stockwell on 22 July.
The other two detainees were arrested around New Southgate on 25 July.
A sixth man arrested as part of the inquiry was not linked with the 21 July attacks and has been charged with wasting police time.
TRACKS OF THE BOMB SUSPECTS
All journeys started between 12:20 and 12:25. Times approx.
OVAL: Man boards northbound Northern Line train at Stockwell and tries to set off bomb between Stockwell and Oval, where he leaves the train. He is chased out of the station at 1235 BST, but escapes towards Brixton.
HACKNEY: Man, identified by police as Muktar Said Ibrahim - or Muktar Mohammed Said - also sets off from Stockwell. Boards Number 26 bus at 1253 at Bank. Police believe he was carrying bomb in a grey and black rucksack, and tried to detonate bomb while on board. Gets off in Hackney Road, near junction with Colombia Road, at 1306.
WARREN STREET: Man who police believe is Yasin Hassan Omar boards Tube train at Stockwell carrying a purple rucksack that they say contained a bomb. Later tries to set off bomb on a northbound Victoria Line train between Oxford Circus and Warren Street, detectives say. Seen without rucksack at 1240 in Warren Street Station before running towards exit and vaulting over ticket barriers.
SHEPHERD'S BUSH: Man wearing dark blue baseball cap and carrying small rucksack enters Westbourne Park Tube station and gets a train travelling towards Shepherd's Bush on Hammersmith & City Line. Tries to set off bomb at 1225 before escaping, probably through window at the end of the carriage, and running along the tracks.