17 Feared Dead In Afghan Crash

U.S. Chinook Chopper Went Down In Mountainous Region

(CBS/AP)  A senior military official believes the 17 American service members aboard a U.S. Chinook helicopter that crashed in Afghanistan on Tuesday were believed to have been killed, CBS News has learned.

The senior Pentagon official spoke on condition of anonymity after the military earlier said the U.S. Chinook helicopter was likely shot down by hostile fire.

The Chinook helicopter was one of four carrying members of a special operations unit into an operation against al Qaeda and Taliban fighters in the rugged mountains near the border with Pakistan when a second helicopter reported seeing an explosion, reports CBS News National Security Correspondent David Martin.

The Taliban claimed it attacked the aircraft and a U.S. military statement said: "Initial reports indicate the crash may have been caused by hostile fire."

The chopper hit a mountain and rolled down a steep slope into a ravine, meaning that not only are 17 special operations force lives at stake, but the small team of American commandos on patrol that called for help might have suffered, Martin reports. The commandos have not been heard from since yesterday before the crash.

With more than 17 probable deaths, this incident could shape up to be the worst loss special operations forces have suffered since the war on terror began.

The coalition and Afghan troops "quickly moved into position around the crash to block any enemy movement toward or away from the site" and coalition support aircraft were overhead, the statement said.

It will take an investigation to determine whether or not this helicopter was, in fact, shot down, Martin said. If it was, this would be the first known instance of a helicopter being brought down by enemy fire. And if that means that the Taliban has figured out a way to shoot down American helicopters, this would be a major new threat, because helicopters are a primary means of transportation along those mountains.

The U.S.-backed mujahedeen war against Soviet occupiers in Afghanistan in the 1980s finally turned when the Afghan fighters figured out how to shoot down Soviet aircraft.

"Coalition troops on the ground in this area came in contact with enemy forces and requested additional forces to be inserted into this operation," U.S. military spokesman Col. James Yonts told a news conference. "That is why there was an aircraft, that is how it arrived on the battlefield."

A Pentagon official told CBS News, "the aircraft, as it was dropping off those personnel, crashed, so we know it was taking fire. Whether that caused it to crash we do not know yet, but it was under indirect and direct fire."

The U.S. military knew from its contacts with local leaders and residents that "terrorist organizations" were operating in the area of the crash, Yonts said.