Huge delays were caused following the crash at junction 30 Erskine Bridge, which happened at about 7.55am his morning.
Five vehicles were initially involved before another 15 were caught up in the collision.
A police spokeswoman said there have been "no reports of any serious injuries," adding: "It's been causing major issues with tailbacks this morning."
The road was closed for investigations to be carried out and for vehicles to be recovered.
Within the last 15 minutes, Traffic Scotland tweeted that the road has re-opened.