The northbound 427 is closed before the westbound 401 off-ramp after a truck carrying gravel rolled over just after noon.
All traffic is being diverted to the eastbound 401.
OPP say the the truck also has a feul leak.
The driver suffered minor injuries.
Police say it's unclear how long clean-up but it could take hours.
The truck appears to have taken out the whole guard-rail and spilled gravel all over the road.
The eastbound 401 off-ramp to Eglinton Ave East is also blocked, as is the ramp from Eglinton West to the westbound 401.