At least two, possibly three, cars were involved in the collision which occurred around 4pm this afternoon.
Police and Trunk Road Incident Support Service (TRISS) attended the scene.
Casualty details have not been released, but early reports suggest no-one was seriously hurt.
Lane 2 westbound remained closed for almost two hours while emergency services conducted a recovery.
Queues stretched back to Livingston for around an hour after the crash.
The road was declared cleared with all lanes reopened at around 5:40pm.
Traffic on the M8 is already expected to be heavier than normal, with Kings of Leon and Britney Spears both playing live concerts in the Glasgow area this evening.
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