New Delhi, April 29 (PTI): NIA has filed a charge sheet against an NSCN-IM militant in connection with the ambush on an army convoy in Arunachal Pradesh on 2 April, 2015, in which three jawans were killed. The charge sheet was filed before a National Investigation Agency Special Court for Arunachal Pradesh at Yupia on Thursday in which NSCN (IM) militant Kapai alias Singmayo Kapai, a resident of Nagaland, has been named as the key accused. NIA told the court that it would continue further investigation in the case as certain other accused are yet to be apprehended, a release issued by the agency here said on Friday.