Defence spokesman Col Rajesh Kalia said that the explosion on board the chopper occurred minutes after its take-off from the Tawang helipad at around 12 noon. The helicopter was en route to Guwahati.
IAF officials said the wreckage of the medium-lift chopper has been located by the Army in Bomdir area.
Three bodies have been recovered so far, Kalia said adding, a search is on for the remaining bodies.
The officials said a court of inquiry has been ordered into the incident.