Hamilton was leading his team-mate Russell through the famous Eau Rouge-Raidillon ascent but the seven-time world champion appeared marginally slower and off-line through the left-right.
Towards the top of the hill, Hamilton drove off the circuit, drifting over the painted run-off before rejoining marginally ahead of Russell, who lifted off the throttle in response.
Hamilton was placed under investigation as a result, and now both drivers have been summoned to report to the race stewards.
Specifically, this is in relation to an alleged breach of Appendix L of the 203 FIA International Sporting Code.
The clause in question reads: "Drivers must use the track at all times and may not leave the track without a justifiable reason.
"For the avoidance of doubt, the white lines defining the track edges are considered to be part of the track but the kerbs are not.
Source: Autosport