The ring road around Brussels (R0) has been closed off in both directions near Haut-Ittre, in the province of Walloon Brabant.
A truck landed on its side, after which a flammable chemical substance leaked onto the road.
The provincial emergency plan is in force.
Anyone going from Wallonia to Brussels will have to take the Brussels ring road via Zaventem, or the E411 motorway.
"For anyone coming from the direction of Halle, the closure would be short-lived," reports VRT Traffic. "From Ittre, the traffic is already being sent to the outer ring."
The Brussels Times