The race at Spa started in drying conditions, heavy rain earlier in the day having cleared but areas of the track still wet.
Proceedings at Spa are overshadowed with the sombre news of Dilano van 't Hoff's death during the Formula Regional race this morning, with no pre-race celebrations and a muted start to the 24 hours.
The Safety Car was due to come in after ten minutes of initial running behind it, however, the #132 GMG Racing Porsche had an incident, going off at turn four and badly damaging the front right of the car, before a green flag could be shown.
Driver Kyle Washington was unharmed, however, the car was out of the race before it had properly started.
The incident caused the Safety Car to be extended while debris was cleared from the top of Raidillon.
Some cars opted to pit for slicks, trusting the track conditions to continue to improve as it crept towards 20 minutes without a green flag.
Racing finally commenced after 23 minutes, with the Huber Porsche holding the lead of the race, Matteo Cairoli at the wheel.
The sky darkened heavily just before the 40-minute mark and race control declared the race under night conditions, despite sunset in Spa-Francorchamps not being due for nearly five hours.
The beleaguered #75 Sun Energy 1 Mercedes, which had been rebuilt following Kenny Habul's crash in pre-qualifying, made its pit lane start with Martin Konrad behind the wheel and progressed to 56th during the first hour.
The #79 Haupt Racing Mercedes, which had started 18th, slipped backwards during the initial race phases, Arjun Maini running in 24th.
It was a similar story for the #23 Grove Porsche, which had started 17th but fell to 31st with Anton de Pasquale as the starting driver, recovering to 27th after the first hour. The #58 Grasser Lamborghini had the worst losses, however, down to 62nd from a seventh-placed start.
At the front of the order, Huber continued to lead with the second-placed #51 AF Corse Ferrari and the third-placed #911 Pure Rxcing Porsche holding their positions from the start.