Police are appealing to the public to hand over mobile phone images, video footage or photographs taken after Thursday's bomb attacks on London.
They believe the footage could provide vital clues as the search for bodies and forensic evidence continues.
As prayers were said for the 49 killed and 700 injured, police insisted: "London is open for business".
Police revealed 1,700 people had already contacted the anti-terrorist hotline since the bombings.
Scotland Yard has set up a special e-mail address, email@example.com, to which the public can send their footage.
Deputy Assistant Commissioner Brian Paddick said: "We believe these images could contain vital information to assist us in the investigation."
Police have released the first pictures of the train at Aldgate
Mr Paddick said some of the calls were "proving to be very, very valuable".
As for the police hunt for the perpetrators, Deputy Chief Constable Andy Trotter said: "Forces from across the country and the world are united in the effort to catch these murderers."
Police say the final death toll is likely to remain at 49.
Emergency teams have removed all the bodies from the train which was blown up between King's Cross and Russell Square, but are continuing to search the carriages to make sure there are no more.
Mr Trotter said all the bodies were now at the mortuary.
"We hope and pray that they don't find any more under there," he said.
'Challenging and demanding'
Forensic teams are continuing their search of the sites of the three underground bombs and Tavistock Square where a bomb tore apart a bus.
Despite Tube closures around the affected lines and road closures around Tavistock Square, police said most transport would be working normally on Monday and urged people to return to work.
Responding to claims by former Metropolitan Police chief Sir John Stevens the bombers were "almost certainly" British, Mr Paddick said no lines of inquiry had been ruled out.
Lord Stevens had said the attackers would not "fit the caricature al-Qaeda fanatic from some backward village in Algeria or Afghanistan".
On Sunday, three people were arrested at Heathrow Airport under anti-terror laws, but no link to the attacks was made. They were later released without charge.
Earlier on Sunday religious leaders issued a statement condemning the bomb attacks.
Sheikh Dr Zaki Badawi, head of the Council of Mosques and Imams, said the assault was "totally contrary to Islam".
The Archbishop of Canterbury Dr Rowan Williams said: "It is a huge fallacy to suppose that one community is somehow more intrinsically prone to violence or outrage than any another."
Anti-terrorist hotline: 0800 789 321
Missing relatives: 0870 156 6344
A service at St Pancras parish church, held near King's Cross underground station where at least 21 people died and Tavistock Square where 13 people were killed by the bus bomb, was attended by hundreds of people.
Father Paul Hawkins said: "This will only make us more determined to live in peace and respect each other and we can all play our part in that."
Meanwhile, it is understood the UK's threat assessment has been returned to its highest level, having been lowered soon after the general election.
Overnight, up to 20,000 people were evacuated from Birmingham city centre following what West Midlands Chief Constable Paul Scott Lee called "a real and very credible threat". The area has now been fully re-opened.
- A two-minute silence will be held at noon on Thursday to remember the victims
- A national memorial to the victims could be built, Culture Secretary Tessa Jowell has said
- Hospitals are treating 65 victims, 15 of whom are in intensive care or described as "critical"
- More than 100 London schools are to reopen on Monday
- Passengers on public transport in London have been warned it is "intolerable" to leave unattended packages or parcels
- British Transport Police has dealt with 22 malicious bomb threats and 150 reports of suspect packages since the attacks
- A reception centre has been opened at the Queen Mother Sports Centre in Victoria, to help the families of people not seen since the explosions
- An emergency call centre has taken more than 120,000 calls.
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