Washington, May 6: American officials said yesterday that it was very likely that a radical group once thought unable to attack the US had played a role in the bombing attempt in Times Square, elevating concerns about whether other militant groups could deliver at least a glancing blow on American soil.

Officials said that after two days of intense questioning of the bombing suspect, Faisal Shahzad, evidence was mounting that the group, the Pakistani Taliban, had helped inspire and train Shahzad in the months before he is alleged to have parked an explosives-filled sport utility vehicle in Times Square.

Officials said Shahzad had discussed his contacts with the group, and investigators had accumulated other evidence that they would not disclose. Yesterday, Shahzad waived his right to a speedy arraignment, a possible sign of his continuing cooperation with investigators.

One senior Obama administration official cautioned that “there are no smoking guns yet” that the Pakistani Taliban had directed the Times Square bombing. But others said that there were strong indications that Shahzad knew some members of the group and that they probably had a role in training him. In a video on Sunday, the Pakistani Taliban claimed responsibility for the attempted bombing.

One issue that investigators are vigorously pursuing is who provided Shahzad cash to buy the SUV and his plane ticket to Dubai, in the United Arab Emirates. “Somebody’s financially sponsoring him, and that’s the link we’re pursuing,” one official said. “And that would take you on the logic train back to Pak-Taliban authorisations,” the official said, referring to the group.

American officials said it had become increasingly difficult to separate the operations of the militant groups in Pakistan’s tribal areas. The region, they said, has become a stew of like-minded organisations plotting attacks in Pakistani cities, across the border into Afghanistan, and on targets in western Europe and the US.