"Some cargo has already moved," CNN quoted an administration official with direct knowledge of the operation as saying.
The official did not reveal detailed information as to what the cargo was or whether it had been moved out by aircraft or ground vehicles.
The recent cargo withdrawal is reportedly intended to show the progress of the Syria withdrawal plan to U.S. President Donald Trump by the Pentagon.
Trump said earlier this week that US troops would be withdrawn from Syria "at a proper pace," while at the same time continuing the fight against the Islamic State (IS).
Currently, there are about 2,000 US troops deployed in Syria.
On Dec. 19, the White House said it would withdraw U.S. troops from Syria after claiming victory in the fight there against the IS. Former US Secretary of Defense James Mattis, who clashed with Trump over the withdrawal issue, signed the withdrawal order days later before leaving office.