A section of an access tunnel underneath the track at Spa-Francorchamps collapsed on Sunday morning.
The Blanchimont Entry Tunnel, which is located just before Paul Frere Corner (formerly Stavelot), provides access from the outside of the circuit to a karting track on the infield. The incident has left a hole in the surface of the run-off on the outside of the corner, though the only damage to the track itself is some cracks in the asphalt.
The circuit was running a Club Subaru Belgium track day on Sunday but the Belgian media reported that there was nobody in the tunnel or on the circuit at the time of the collapse.
The tunnel was built in 1978, with the last remodelling of the Spa circuit - just beyond Blanchimont - taking place in 2007.
Spa is scheduled to host the Belgian Grand Prix on August 27-29 this year. The circuit was only due to hold test and track days in the coming weeks, ahead of the visits of Formula Renault 3.5 on May 1-2 and the Le Mans Series on May 8-9.