A British newspaper says one of the suspected London suicide bombers was investigated by the domestic intelligence agency last year, but in the end was not considered a threat.
The Sunday Times reports that MI-5 had checked out Mohammad Sidique Khan, but did not put him under surveillance. British officials had no comment.
A photograph showing the four suspected bombers entering a rail station together the morning of the attacks appeared in Sunday papers, and officials hoped this might create new leads.
Meanwhile, Pakistani investigators were reportedly tracing a list of telephone calls to Pakistan by some of the suspected suicide bombers. And in Cairo, the investigation continued into an Egyptian biochemist who left Britain four days before the bombings. British officials suspect a connection to the attacks, but Egyptian officials question this.
Some information for this report provided by AFP and Reuters.