Police said on Monday they were questioning relatives and friends of three suspects held over the failed British car bombings but had made no formal arrests.
Police Commissioner Achyuta Rao said they were examining the contents of "high-capacity" CDs seized from the homes of two Indian suspects from Bangalore's Jayanagar district who were linked to the terror plot in Britain.
"Nobody has been arrested as yet. Investigations are continuing," he told a press conference in Bangalore.
Kafeel Ahmed, an aeronautical engineer, is believed to be one of the two men who drove a blazing Jeep Cherokee into Glasgow airport. His brother Sabeel, a doctor, is also being investigated by British police.
The botched attack in Scotland came after two failed car bombs in central London on June 29.
No "confessions" from the suspects' family members, friends or associates had been recorded but they were still being questioned, Rao added.
The third Indian suspect has been identified as Mohammed Haneef, a doctor working at hospital in Australia's Gold Coast where he relocated from Britain last September.
Haneef, a cousin of the Ahmed brothers, was detained as he attempted to leave Australia for India on a one-way ticket.
A report on Sunday in the Hindu newspaper said Kafeel Ahmed began researching bomb-making techniques weeks before he travelled to Britain on May 5.
Findings by investigators suggest that Kafeel Ahmed acted without training or material assistance from organised groups, the report said, adding the police had found no evidence of him being linked to militant organisations.