Police are hunting the London bombers' accomplices, as it emerged explosives found in Leeds are similar to those used in other al-Qaeda-linked attacks.
Explosives in a house are thought to have been made from ingredients available from high-street chemists.
Police are hunting the London bombings mastermind, and an Egyptian chemistry student who has fled his Leeds home.
Detectives said they wanted to know who had "supported, financed, trained and encouraged" the bombers.
A man injured in last the bus bombing in Tavistock Square died in hospital on Thursday, taking the overall death toll to 54.
Police say three of the four bombers thought to have died in the attacks are included in this figure and they are currently searching the bombers' homes.