The Belgian Grand Prix was red-flagged to a halt on the opening lap on Sunday after a spectacular first lap crash that saw Fernando Alonso and two others unable to continue.
The Safety Car was deployed immediately, but no drivers were injured after Nico Hulkenberg of Renault drove into the rear of Alonso's McLaren.
The Spaniard's car was sent spiralling into the air, narrowly clearing the cockpit of Charles Leclerc's Sauber car.
This crash triggered a multiple collision that saw damage to other cars including Daniel Ricciardo's Red Bull, who hit the rear of Kimi Raikkonen's Ferrari.
As the carnage was cleared, Alonso, Leclerc, Hulkenberg and Ricciardo were left with the most most-damaged cars.
All but the Australian were forced to retire.
At the front, championship leader Lewis Hamilton started from his record fifth Belgian pole in his Mercedes, but was passed by championship rival Sebastian Vettel of Ferrari who drafted past him on the Kemmel Straight to take the lead before the Safety Car was deployed.
The race resumed on lap five with Vettel resisting an immediate attack from Hamilton when the Safety Car pulled in.