The British press says 16 bombs have been found in a car in Luton, abandoned by the July 7 London bombers.
In another major development, one of the suspected July 21 would-be bombers has been captured. Yasin Hassan Omar was one of several men arrested on Wednesday in raids in central England.
Three women have also been arrested in Stockwell, London, accused of sheltering terrorists.
Anti-terrorist police chief Peter Clarke confirmed Omar’s arrest in a press conference.
“You will be aware that in the early hours of today, four men were arrested in Birmingham,” he said.
“A number of house searches are taking place. I can confirm that one of the men who has been arrested is Yasin Hassan Omar.”
Scotland Yard meanwhile released a new picture of one of the three other suspected bombers being hunted after last week’s bid to carry out fresh attacks on London’s public transport system. As Britain’s biggest ever manhunt continues, police once again warned that,until caught, the three men remain a threat.