Phone calls had been made to some Pakistanis from the house of one of the bombers. Three of the four attackers were British nationals with Pakistani roots.
The British government gave Pakistan the names and telephone numbers of some individuals after the 7 July attacks that killed 55 people, a security official on Monday told reporters on condition of anonymity.
Security officials said they interrogated six people about their links to the family of Shahzad Tanweer.
"We have established that these people had business contacts with the family of Tanweer back in London," a senior security official said.
"The six 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 three bombers recently visited Pakistan and investigators are determining whether they met al-Qaida-linked groups.
A senior immigration official in Karachi said Tanweer, 22, and Mohammad Siddique Khan, 30, flew to Karachi on 19 November and left on 8 February for Britain.
Linking the bombers
Hasib Hussain, 18, arrived in Karachi on 15 July, 2004, from Riyadh. The immigration official said there was no record of him leaving Karachi but he could have flown out via Lahore or Islamabad.
"The six interrogated are all cleared now. The telephone calls were made only for business purposes and were not linked in any way to the attacks"
"So far we have not found the links of Tanweer and Khan to Hussain, but it could be possible that they were on different
assignments," a Karachi-based intelligence official told reporters.
Foreign ministry spokesman Jalil Abbas Jilani, however, said he had no information that the three bombers had travelled to Pakistan.
Pakistan's ambassador to the United Nations Munir Akram said on Sunday that Britain should not blame foreign countries including his own for the attacks but should look into its own failure to integrate Muslims.
"It is important not to pin the blame on somebody else when the problem lies internally," Akram told BBC Radio.
"I think you have to look at British society, what you are doing to the Muslim community and why is it that the Muslim community is not integrating into British society."