Investigation authority expanded: designated income tax officers may probe persons regarding tax treaty agreements even without pending proceedings. The amendment inserts a provision authorizing an income tax authority not below the rank of Assistant Commissioner, as notified by the Board, to exercise the powers of inquiry or investigation in relation to any person or class of persons concerning agreements referred to in tax treaty provisions, notwithstanding that no proceedings are pending before that or any other income tax authority; and it consequentially includes this new subsection within the enumerated provisions governing exercise of those powers.