A collision on the southbound A40 near to the Gibralta tunnels has led police to divert traffic off at Beech Road.
Gwent Police are advising motorists to find an alternative route until the road is cleared.
Traffic is building up at the Beech Road turnoff as all traffic is being re-directed.
The a40 is now closed between Monmouth and Raglan
Diversions are in place which may cause congestion.