One major mover keeps coming up in all the AFP interviews -- Assad's much-feared brother Maher, the de facto head of Syria's elite unit, the 4th Division.
A dozen sources told AFP that the division was deeply involved in the trade, including smugglers, a regional law and order official, a former Syrian intelligence officer, a member of a tribe that smuggles captagon and a pharmaceutical industry insider.
The British Army-linked CHACR think tank and the independent Center for Operations Analysis and Research (COAR) have also pointed the finger at Assad's brother.
"Maher al-Assad is one of the main beneficiaries of the captagon trade," said Rami Abdel Rahman, director of the UK-based Syrian Observatory for Human Rights.
"He receives his own share from the profit. Drug money has become a main source to pay the salaries of an armed group affiliated with the 4th Division," he added.
Some captagon labs get "the raw material directly from the 4th Division, sometimes in military bags", said a Syria monitor, with a trafficker telling AFP that it even supplied rebel groups opposed to the regime.
The division controls large parts of the porous border with Lebanon that is key to the trade, with the Mediterranean port of Latakia another of its bastions.
Caroline Rose, of the Washington-based Newlines Institute, said it has "played an active role in guarding, facilitating and running a lot of captagon in Homs and Latakia" and then "transporting shipments to state-owned ports".
The Syrian interior ministry said that drug traffickers and "terrorist" groups, who "benefited from their control over the border areas," were behind the country's booming trade.