TV footage showed Goolaerts, 23, receiving CPR treatment from medics by the side of the road after crashing.
Shortly after the 257-km race ended, Paris-Roubaix director Christian Prudhomme told Reuters that Goolaerts had to undergo a scan at the Lille hospital.
"His situation is still very worrying," Prudhomme, who is also the Tour de France director, added.
His team, Veranda’s Willems-Crelan, said in a statement that Goolaerts had been taken to hospital having been involved in a crash.
They later appealed for people to refrain from speculation as they wait for an update on his situation.
"Our thoughts are with his family and friends now," the team said.
(Reporting by Julien Pretot; Editing by Toby Davis)
