United States and British authorities investigating the deadly subway attacks in London are searching for information on Haroon Rashid Aswat, a Pakistani allegedly connected to a foiled plot to create a terrorist training camp in remote Bly in US state of Oregon.
Aswat's cell phone received as many as 20 calls from several bombers, said intelligence and law enforcement officials.
The last call was made in London the night before the July 7 bombings, officials said.
Authorities in the US, Britain and Pakistan said on Thursday they do not know what role Aswat may have played in the attacks, and whether he was the one using the cellphone or when he may have been in London last.
Aswat, 31, grew in Batley, a rough-and-tumble town in north-central England, nicknamed 'the Bronx' and brimming with immigrants from India and Pakistan.
US authorities first heard of him while investigating attempts by Muslim extremists to set up a training camp in the Oregon woods in 1999.
Aswat was an aide then to Hamza Masri, a fiery Muslim preacher who was arrested in April 2004 and charged with a variety of terrorism-related offences, including involvement in the Oregon camp.
In recent years, US officials have even wondered whether he is alive because of unconfirmed reports that he was killed in Afghanistan, according to The Washington Post.
There is some evidence, according to an official involved in the investigation, that Aswat may have left Britain on a ferry two weeks ago, suggesting that he left his cellphone behind for accomplices to use.