Update 6pm: A woman has been taken to the Royal Gwent Hospital.

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Update 5.43pm: Long delays are still being reported on the M4.

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Update 5.32pm: Travel delays have increased to one hour.

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Update 5.05pm: All lanes have now re-opened.

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Update 5pm: Delays to travel are roughly 55 minutes.

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Update 4.45pm: There are reports that the build-up of traffic is miles long.

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THREE lanes are blocked on the M4 following a crash.

The incident happened just before the Brynglas Tunnels.

All lanes are blocked on the one side.

A spokeswoman from Welsh Ambulance said: "The crash happened just before the Brynglas Tunnels.

"We have one ambulance at the scene."