The officials said British investigators asked Pakistani authorities to search for Haroon Rashid Aswat, who reportedly had been in close contact with the suicide bombers just before the attacks.
Aswat reportedly was once an associate of Abu Hamza al-Masri, a radical imam awaiting trial in Britain on charges of incitement to murder. Al-Masri also is wanted in the United States on charges of trying to establish a militant training camp in Bly, Ore.; involvement in hostage-taking in Yemen; and funding militant training in Afghanistan.
Quoting unidentified intelligence sources, The Times of London said Aswat visited the hometowns of the four London bombers and selected their targets. It also reported there had been up to 20 phone calls between Aswat and two of the bombers before the attacks.
Aswat's relatives in Batley, near the northern England town of Leeds, which was home to two of the suicide bombers, said they had not heard from him for many years.
"He has not lived at this house and we have not had contact with him for many years," said his father, Rashid, who asked for his family to be left in peace. "There is no story that we can provide."
Authorities are investigating whether the London bombing suspects, three of whom were of Pakistani origin and traveled to Pakistan last year, received training or other assistance from militants in that country.
One of the July 7 bombers, Shahzad Tanweer, 22, is suspected of visiting a madrassa linked with militants in Lahore that has become a focus of the inquiry.
A Pakistani newspaper reported that Tanweer revered Osama bin Laden. The English-language newspaper Dawn said Tanweer visited relatives in November in a farming village near Faisalabad in eastern Pakistan. During his stay, he was visited by another bombing suspect, Mohammed Sidique Khan, 30, Tanweer's uncle told the newspaper.