UPDATE 4pm: All lanes have been re-opened on the M4 following the earlier accident.

Despite the lanes re-opening, there is still congestion back as far as junction 23 on the westbound carriageway.

UPDATE 3.40pm: Two lanes remain closed on the M4 westbound, and there are severe delays of 35 minutes between the Prince of Wales Bridge and junction 24 A449 (Coldra).

On the eastbound carriageway, traffic seems to have returned to normal.

UPDATE 2.37pm: The M4 westbound carriageway traffic queue is around eight miles long, and travel time through it is currently estimated at an hour.

Two lanes remain closed at the site of this morning's crash, between junctions 24 (Coldra) and 25 (Caerleon).

UPDATE 2.16pm: Westbound traffic is queuing back several miles to junction 23 (M48/Chepstow) as only one lane is open past the scene of the crash.

South Wales Argus:

Westbound M4 traffic approaching junction 24 (Coldra) this afternoon. Picture - Traffic Wales

Eastbound M4 traffic remains heavy back to junction 28 (Tredegar Park), but is moving more freely.

UPDATE 2.05pm: The A48 Southern Distributor Road remains very busy, particularly eastbound approaching the Coldra (M4 junction 24), and around Newport Retail Park.

UPDATE 1.46pm: Police are appealing for any witnesses to the crash to get in touch, and are specifically interested in hearing from anyone who has dashcam footage, and who were travelling along the M4 between junctions 24 and 25 shortly after 11am this morning.

Contact Gwent Police by telephoning 101, or by direct message on the force Facebook and Twitter pages, quoting log number 116 03/01/20.

UPDATE 1.21pm: This morning's crash involved one vehicle, not several, as reported earlier. 

The incident happened at 11.05am and involved a silver BMW.

A 70-year-old man from the Raglan area has taken been to University Hospital of Wales in Cardiff.

The M4 westbound between junctions 24 and 25 has partially reopened, but traffic remains heavy in both directions.

UPDATE 1.07pm: The eastbound carriageway of the M4 is now open, according to Gwent Police, and there is one lane open on the westbound carriageway, which is likely to cause congestion.

UPDATE 12.57pm: All lanes have now been reopened following the crash.

Traffic is still extremely slow both ways on the M4, with queues back to junction 23 westbound, and junction 29A (A48M) eastbound.

UPDATE 12.50: One man has been taken to hospital with a head injury, according to Gwent Police.

A silver BMW is understood to have been involved in the incident.

UPDATE 12.44pm: The incident is being described by AA Travel as "a multi-vehicle accident".

UPDATE 12.42pm: Eastbound M4 traffic is being taken off at junction 26 (Malpas).

UPDATE 12.37pm: South Wales Argus:

Standstill on the bridges across the M4. Picture - Johnathan Grimes

UPDATE 12.30pm: Routes into and out of Newport - including Chepstow Road, Malpas Road, and the A48 SDR - are increasingly busy as a result of the crash.

The motorway is backed up westbound to junction 23A (Magor services, A4810), and eastbound to junction 28 (Tredegar Park).

Avoid the area if possible, and whatever alternative route you take, allow extra time for your journey.

UPDATE 12.24pm: The air ambulance is at the scene.

South Wales Argus:

Picture: Grace Young

UPDATE 12.11pm: Traffic is being held for at least half an hour.

All the traffic that can be, is being directed off the motorway at junction 24 (Coldra). As a consequence, the A48 Southern Distributor Road is getting busy, especially around the Newport Retail Park/Spytty area.

UPDATE 12.06pm: Traffic is at a standstill both ways on the M4 while the emergency services deal with the incident.

Queues are back beyond junction 27 (High Cross) eastbound, and back towards junction 23A (Magor services, A4810) westbound.

UPDATE 11.53am: All traffic is now being held temporarily both ways from junction 24 (Coldra) to 25 (Caerleon).

Police, fire and ambulance services are in attendance.

Eastbound, the queues are back to junction 26 (Malpas).

A CRASH has closed a lane of the M4 around Newport, westbound between junctions 24 (Coldra) and 25 (Caerleon).

Traffic is very slow and backing up on the approach. The outside lane is closed and South Wales Fire and Rescue are at the scene.