New Delhi, Jan 18: Salwinder Singh, the former Gurdaspur SP who is being probed for any possible link with the Pathankot airbase attackers, has been "cooperating well" with the tiol Investigation Agency (NIA), official sources told IANS on Monday. According to the sources, the investigators have so far found nothing "incrimiting" that could link Salwinder with the Pathankot terror strike.