The deputy governor of Kunar Province, Noor Mohammad, said hundreds of Afghan security forces also have been deployed in the towns and villages of the province while the recovery operation continues.
"We do not know exactly what caused this crash," Noor Mohammad said. "But most probably it seems to be from an enemy attack. We have deployed hundreds of policemen. Also, an investigation is going on to find out what happened exactly and who was behind this attack."
U.S. Marine Corps General Peter Pace was asked about the crash during a hearing yesterday in Washington of the U.S. Senate's Armed Services Committee.
"We think it was a rocket-propelled grenade, sir," Pace said. "But [we are] not 100 percent sure. And that will come out in time as we are able to get to the scene and do the investigation required."
In Afghanistan, a spokesman for U.S.-led coalition forces, Colonel James Yonts, said the Chinook crashed while taking part in a mission against Al-Qaeda fighters called Operation Red Wing, near the Afghan-Pakistan border.
He said the Chinook was one of two helicopters carrying commando teams into the remote mountains to reinforce U.S. troops engaged in a battle against militants.
"Coalition troops on the ground in this area came in contact with enemy forces and requested additional forces to be inserted into this operation," Yonts said. "That is why there was an aircraft. That's how [the helicopter] arrived on the battlefield."
Military analysts said the Chinook might have flown into a trap set by Al-Qaeda and Taliban fighters. Militants have become accustomed to seeing U.S. troops being reinforced by the bulky and low-flying Chinooks.
"Taliban and Al-Qaeda forces would be well aware of the importance and the vulnerabilities of aircraft such as the Chinook within U.S. strategy," said Ian Kemp, an independent defense analyst based in London. "This isn't peculiar just to U.S. forces. Throughout the 1980s, the Soviets relied heavily upon helicopters to provide mobility for their forces. Hence, the reason that the United States supplied Stinger [surface-to-air missiles] to the mujahedin. And, of course, that's the reason that the United States was so keen to get those Stingers back at the end of that conflict -- because they knew these Stingers would eventually pose a threat to their own helicopters and also to civilian aircraft."
Kemp said investigators must examine the wreckage, but noted that a rocket-propelled grenade or a surface-to-air missile like the Stinger would be capable of shooting down a Chinook.
"It was a major concern during the invasion of Afghanistan following [the attacks of 11 September 2001] as to how many Stingers that the Taliban and Al-Qaeda forces might have -- bearing in mind that these missiles are getting quite old now," Kemp said. "But certainly, the RPG-7 and more sophisticated versions of the RPG have proven to be very effective, indeed, in engaging helicopters at low altitudes. And this is demonstrated in a number of situations [like] Somalia and Iraq."
Rohulla Anwari, RFE/RL's correspondent in Kunar Province, quoted Afghan witnesses as saying they saw the wreckage of a Chinook being airlifted through the narrow valley that includes Kunar's provincial capital of Asadabad. The witnesses said the Chinook was in a sling beneath a large U.S. cargo helicopter.
U.S. military officials have declined to comment on the report, saying Al-Qaeda fighters remain active and that military operations are still under way.
(RFE/RL Afghan Service correspondent Sultan Sarwar contributed to this report.)