Police investigating last Thursday's London bomb attacks have found explosives in a car parked at Luton railway station in Bedfordshire.
Police earlier said they have strong evidence that at least one of the four suspect bombers died in an attack on the underground at Aldgate Station.
They have also found personal belongings linked to the men at the different blast scenes.
Police say CCTV shows the four suspects arrived together by train in the capital on the morning of the attacks.
One man has been arrested in West Yorkshire after early morning raids by anti-terrorist officers on several premises in Leeds and has been taken to London for questioning.
Arrest warrants have also been issued for six others.
A controlled explosion was also carried out by army bomb disposal experts at a house in the city. The house is one of six addresses raided by police.
Up to 600 people were evacuated from the area as part of the operation.
US decision on troops reviewed
Britain's Defence Secretary, John Reid, earlier said a US decision to ban its British-based military personnel from London in the wake of last week's attacks was being urgently reviewed.
In a television interview, Mr Reid said the decision was being re-considered, and that the US government had offered its full support.
Up to 10,000 US military personnel based in Britain had been banned from visiting London until further notice because of the fear of more attacks.
London's Mayor, Ken Livingstone, and other political leaders have said people should not be cowed by terrorism.
Death toll expected to rise
As the search for bodies at King's Cross underground station continues, the death toll from the attacks is expected to rise.
The tunnel between King's Cross and Russell Square underground stations is now the only remaining site where the search for the dead is still going on.
The task of workers there has been made slightly easier - and cooler - by the removal of airtight seals which had protected potential forensic evidence in the tunnel from contamination.
The bomb had been left on the floor of the carriage and the search is now concentrated on the track under the train.
