The Army helicopter shot down over Iraq (search) last weekend apparently had a last-second warning of an approaching missile and managed to launch flares designed to draw the heat-seeking missile away, a senior Army official said Thursday.

The Pentagon, meanwhile, announced that one of the soldiers injured in the attack died Thursday at a medical facility in Germany, raising the death toll to 16. Twenty-six others were injured.

It is not clear why the defensive moves did not work, but the official, who discussed the attack investigation on condition he not be identified, said U.S. officials believe the shooter simply got in a "lucky shot."

The helicopter was flying at between 200 and 300 feet, he said -- meaning that the fast-moving missile, when fired at the correct angle of approach, allowed little time for its target to escape.

Two missiles were fired. One slammed into the right side of the helicopter's rear engine, causing it to fail catastrophically and triggering a fire.

All three crew members perished.

The exact type of missile used has not been determined, the Army official said, although it is known to have been of the shoulder-fired variety, also known as a man-portable air defense missile. Speculation has centered on the SA-7 (search), a Russian-designed missile widely available in Iraq.

The official said a number of survivors, Iraqi eyewitnesses on the ground and passengers aboard a second Army helicopter flying nearby reported having seen flares after the missile was launched. The official stressed, however, that he considered this information to be unconfirmed.

The investigation is likely to continue for many weeks, the official said.

The attack was the single deadliest of the war for American forces. It triggered questions from some members of Congress about whether the Army was adequately equipping its helicopters against threats like shoulder-fired missiles of the sort apparently used to bring down the CH-47D Chinook (search).

U.S. military officials said on Tuesday that the Chinook in question was equipped with an ALQ-156 missile alert system (search), as is standard for the entire Chinook fleet. But it had not previously been disclosed whether the alert system functioned and whether flares were dispensed.

The destroyed Chinook was operated by pilots of the Illinois and the Iowa National Guard, attached to the active-duty 12th Aviation Brigade. It was a 1991 model and was ferrying soldiers to Baghdad; some were due for short R&R breaks in Baghdad, others were headed out of the region for two-week breaks.

The Army official said the Chinook had not only an ALQ-156 missile warning system but also an APR39V radar warning system (search). The ALQ-156 system is linked electronically with the flare and chaff canisters, and can be set either to automatically or manually dispense them once a missile is detected. The official said he could not disclose whether it was in automatic mode at the time but described the system as "operational."

"The aircraft had what is required to defeat the threat over there," the official said.

Some Chinooks in Iraq are equipped with a different missile alert system, called the ALE-47, the official said. He insisted that while different in function, the ALE-47 is not necessarily more effective against all missile threats.