Broeckx underwent two operations to stabilise intercranial pressure on Tuesday and remains in the coma to let his body recover from his injuries.
The team report that no prognosis can be made at this point.
It is the second time that Broeckx has been injured in an incident involving a race motorbike this season, having broken his collarbone after being knocked off at Kuurne-Brussels-Kuurne.
Saturday’s stage of the Belgium Tour was cancelled when the severity of Broeckx’s injuries became apparent. It is believed that a motorbike crashed into another motorbike and then collided with a group of riders.
The peloton held a protest at the start of the fourth stage of the race to highlight the need for increased rider safety in races. The UCI says it will increase human resources at races to ensure guidelines for race vehicles are strictly adhered to.