**UPDATE: 6.10pm**

THE incident is continuing to cause congestion, with slow traffic from Junction 29.

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THERE have been long delays on the M4 after an accident left one lane blocked.

Two cars were involved in the collision on Junction 27 eastbound, near High Cross.

The incident has left tailbacks to Junction 28.

There were no serious injuries and South Wales Ambulance Service were not called to the scene.