An access tunnel underneath a section of track near Spa-Francorchamps' famous Blanchimont corner has partially collapsed.
Local reports said no cars were circulating the Belgian GP venue at the time of the collapse, and that the only damage to the surface itself is some cracks.
It is not believed anyone in the vicinity of the tunnel, which despite recent renovations at the circuit dates back to the 70s, was hurt.
The collapsed tunnel, providing access to trucks and also pedestrians, was 6 metres in height. Damaged in the collapse was some run-off area, guard rails and a television camera.
Spa, scheduled to host formula one in late August, will be closed this week due to the collapse.