A Welsh Government spokesperson said the pothole was around one metre by one metre.
All repairs were carried out and the lanes re-opened within 90 minutes.
The cause of the damage is being investigated.
The motorway has now fully re-opened.
A LARGE pothole has appeared in the M4 in Newport this morning causing two lanes to be closed as repairs are made.
The repairs are being made between High Cross and Tredegar Park where the two lanes are closed.
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Congestion is stretching back to J26 at Malpas.