UPDATE: 7.25pm Crews rescued the second horse and both were led to replacement horse boxes suffering with minor cuts and bruises.
UPDATE: 7.13pm Jennie Griffiths, from the South Wales Fire and Rescue Service said one horse was led to safety and a second was trapped. Two people were treated at the scene.
UPDATE 3.08pm: The road has now been cleared and traffic is flowing freely again.
UPDATE 1.52pm: Traffic is currently queuing for miles eastbound, back to junction 24 (Coldra).
TWO lanes of the eastbound carriageway of the M4 between junction 23 for Rogiet and the second Severn Crossing are blocked as the result of an overturned horse box.
Traffic is currently queuing back eastbound to around a mile before Magor services.
The M48 Severn Bridge is closed all weekend for roadworks, so drivers have no choice but to use the second crossing to travel from South Wales into England.
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