The US investigators probing Mumbai attack have concluded after quizzing the lone captured terrorist Ajmal Amir Kasab that there was no involvement of Inter Services Intelligence in the carnage. According to sources, Federal Bureau of Investigation personnel were allowed to interrogate Kasab for nine hours during which they were able to establish that he was a Pakistan national. The source said FBI investigations have further established that the attackers had reached Mumbai from Pakistan, where the plan was allegedly hatched and the terrorists were provided necessary training by Laskar-e-Taiba. Based on Indian example of allowing FBI to probe Kasab, the US and UK are now pressuring Pakistan to allow their investigators to grill those arrested by Pakistani authorities. Besides, the renewed US pressure on Pakistan government to rein in ISI, the sources said, was because of previous involvement of ISI in 'questionable activities'.