Many are reported to have left since the Kurdish forces, who previously guarded the camp, withdrew.
Al-Hol is Syria's largest detention camp for suspected ISIS supporters, and has been home to around 24,000 people, most of them women and children. Around 15,000 were Syrians, several thousand were Iraqis, and more than 6,000 were from around 40 other countries.
According to the source, there have been "no more than 20 families in the foreign annex" since Saturday.
The Kurdish-led forces stated in January that they had been forced to withdraw from al-Hol, while the army accuses them of abandoning it.
