"He is no longer at Fleury-Merogis," the source told AFP, referring to the jail on the outskirts of Paris where Abdeslam was imprisoned.
A convoy of tactical police vehicles left the prison between 3:30 and 4:00 am (0230-0300 GMT), according to an AFP reporter, although it was not possible to identify the passengers.
The Brussels trial revolved around a gun battle in the Belgian capital on March 15, 2016, four months after the Paris attacks, which led to Abdeslam's capture days later. Three police officers were wounded and a fellow jihadist was killed.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)