"We have established that these people had business contacts with the family of Tanweer back in London. The six persons interrogated are all cleared now. The telephone calls were made only for business purposes and they were not linked in any way to the attacks," The News quoted a Pakistani senior security official as saying.

He further said that the three bombing suspects - Hasib Hussain (18), Shahzad Tanweer (22) and Mohammad Siddique Khan (30) - traveled to Karachi last year. However, he failed to comment as to which areas they visited, and what was the purpose of their visit.

The security official also denied that Pakistani authorities had made any arrests relating to the London attacks.