All U.S. forces have been removed from Bagram Airfield, the largest military base in Afghanistan, a senior U.S. official told Fox News Thursday.

Bagram Air Base, located just north of Kabul, was the heart of the U.S. operation in Afghanistan for nearly 20 years following the attack on Sept. 11, 2001, by Al Qaeda, which was based in the country.

U.S. officials announced last week that the United States was more than 50 percent finished with packing up the roughly 30-square-mile base. European troops had largely pulled out months ahead of the U.S. departure from what was a stronghold in the war on terrorism.

Italy and Germany declared their missions in Afghanistan complete Wednesday. The Bagram Air Base will be taken over by Afghan forces to continue the fight against the Taliban.

The U.S. military is expected to remain involved in Afghanistan until its final departure by September 11 and will help Afghan forces with operations through airstrikes, officials said Thursday.

A contingent of 650 U.S. troops will remain in Afghanistan indefinitely, based largely at the U.S. embassy for diplomatic security. Another 300 troops could remain behind through September at Kabul Airport for additional security measures.