The troops were on a mission in the Shah Wali Kot district of Kandahar Thursday morning when the helicopter, a Blackhawk UH-60, went down. Three Afghan troops and one Afghan civilian interpreter were also on board and died in the crash.
Two U.S. military officials told ABC News they are "leaning toward" believing the helicopter was shot down.
As soon as it crashed, enemy combatants headed for the site. A second U.S. helicopter arrived and the enemy was repelled from the air.
The Taliban has claimed responsibility for the attack, saying one of its fighters shot down the aircraft. The International Security and Assistance Force in Afghanistan would not confirm the aircraft had been shot down, but two hours before it announced the crash, a Taliban spokesperson tweeted that it had been shot down. The Kandahar governor's office also sent out a tweet referring to the aircraft as being "shot down."
"This happened in the enemy's backyard," said a U.S. military official.
The bodies of the seven Americans and four Afghans killed in the crash have all been recovered.
"I offer my sincere condolences to the loved ones and friends of 10 of these brave service members and their civilian colleague who lost their lives today," ISAF spokesman Brig. Gen. Gunter Katz said today in a videotaped statement.