Lt. Col. Bartolome Bacarro, Armed Forces public information chief, said these samples would be thoroughly examined to determine the cause of the crash.
"Some parts of the helicopter have been brought to the 14th Maintenance Wing of the Philippine Air Force in Clark Field," he said.
Bacarro said Air Force investigators at Mactan Air Base and Clark have yet to come up with a conclusive report as to why the decades-old helicopter went down.
"As of now, there are no clear as well as conclusive reports that could tell us the reason for the helicopter crash," he said.
Bacarro said investigators cannot say if the nylon cord which they found entangled in the helicopter’s rotor caused the crash.
In two or three days, investigators would come out with their partial report, he added.
Bacarro said the helicopter piloted by Capt. Allan Villagarcia, with Lt. Jesus Ermal as co-pilot, along with gunners Sgt. Michael Gavino and M/Sgt. Johnny delos Reyes, was conducting "touch and go" exercises.
"They were conducting a pre-qualification flight, and the chopper was approaching a ‘touch and go’ point when it suddenly encountered a problem," he said.
"Touch and go" flying is a military technique of ferrying troops to combat zones without landing sites using transport and attack helicopters, he added.
Bacarro said investigators gathered that Villagarcia was training Ermal on the workings of "touch and go" flying at the time of the exercise.
"There’s an investigation being conducted," he said. – Jaime Laude, Denise Limson, Sheila Francisco