The first victim of the London bombings has been named, as the confirmed number of dead reached 52.
Susan Levy was a mother of two grown-up sons
An inquest was opened and adjourned into the death at King's Cross of Susan Levy, 53, from Cuffley, Hertfordshire.
As families of the missing continued to seek information, Tony Blair said a memorial service would be held and attended by the Queen at some point.
Metropolitan Police Commissioner Sir Ian Blair said those responsible for Thursday's attacks would be found.
In a statement to the House of Commons, the prime minister confirmed a two-minute silence would be held at noon on Thursday. The date of the memorial service would be named after consultation with victims' families, he said.
The Mayor of London, Ken Livingstone, also announced the opening of a memorial fund set up with the Red Cross, which has already donated £50,000 to help victims and their families.
Mr Blair promised one of the most "vigorous and intensive" police manhunts the UK has ever seen to catch those responsible for the bombings.
He said the government expressed its "revulsion" at the "murderous carnage of the innocent".
Police said they had established the identities of most victims who had been recovered, but they said the number of dead could still rise.
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Scotland Yard said a strong public response was helping its inquiry.
During his visit to King's Cross station, Sir Ian Blair appealed to the public to give investigators time, saying they were dealing with the "biggest crime scene in English history".
Describing the scale of the investigation, he said officers had so far collected 2,500 CCTV tapes, taken 2,000 calls via the anti-terrorism hotline and were dealing with 115,000 calls to the casualty bureau.
But he vowed: "These people will be caught."
The commissioner said he would be taking the underground back to work and advised people to travel by Tube, while remaining vigilant.
A book of condolences was opened at City Hall in London on Monday and public transport was once again busy.
Transport for London said there were six bomb alerts on the Tube and at least as many on the capital's buses, but police said it was better for people to report suspicious packages than keep quiet.
With the formal process of coroners identifying those killed now under way, Scotland Yard said it had informally identified the first 49 known victims through information found on their bodies, or relatives coming to see them. Three have been formally identified.
Mrs Levy's husband, Harry, said: "We are all distraught at her needless loss and our thoughts and prayers are also with the many other families affected by this horrendous tragedy."
She had travelled to London with one of her two grown-up sons, before they went their separate ways for work.
Uncertainty remains for many families, with many continuing to appeal for news about missing loved ones.
The mother of Anthony Fatayi-William, 26, who worked in London for an oil company, believes he may have been a passenger on the number 30 bus that exploded in Tavistock Square.
After travelling from Nigeria to look for him, she said: "This is now the fifth day, five days on, and we are waiting to know what happened to him. I am his mother, I need to know what happened to him."
First to sign the book of condolences was Mr Livingstone, who wrote: "The city will endure. It's the future of our world. Tolerance and change."
He was followed by politicians, faith leaders and Sir Ian.
A garden of remembrance at Victoria Embankment Gardens has attracted hundreds of floral tributes and messages.
Flowers have also been laid at King's Cross station and another memorial flower garden is planned for Russell Square, near the scene of one of the underground blasts and the bus explosion.
Police and security agencies say they are now almost certain they are not dealing with a suicide bomb attack.
In his statement, the prime minister said it was probable "Islamist extremist terrorists" carried out the attack, but added: "People know full well that the overwhelming majority of Muslims stand four square with every other community in Britain."
He said he knew of no intelligence specific enough to have prevented the attacks.
Security officials have searched the flat of a British man living in Poland, in relation to the attacks. No arrest has been made.
Anti-terrorist hotline: 0800 789 321
Missing relatives: 0870 156 6344
Between Aldgate and Liverpool Street tube stations
Between King's Cross and Russell Square tube stations
At Edgware Road tube station
On bus at Tavistock Square