A large section of the M4 motorway in south Wales has been closed off following a crash involving a tanker and several vehicles.
Emergency services were called to the scene between junctions 32 and 33 near Cardiff after a tanker hit the central reservation.
South Wales Fire Service said it is attending the scene alongside police and ambulance crews.
A spokeswoman said: "The incident involves multiple vehicles - including a tanker, van and several cars."
The alarm was raised at around 5.50pm - and has seen the westbound carriageway of the M4 closed near Cardiff and one lane closed on the eastbound side.
Motorists stuck in the ensuing queues said they saw lots of emergency crews en route to the crash.
Twitter user James Allen wrote: "Must be such a bad accident on the M4 haven't moved for over half hour and 10+ fire engines, police cars and ambulances have flown past."
The Welsh Ambulance Service said it has sent two rapid rapid response vehicles, one ambulance and a doctor.
However, an ambulance could not be called in due to poor weather conditions.
Diversions have now been put in place at junction 30 - more than 10 miles from the crash site.
South Wales Police has since advised motorists to steer clear of the M4.
The Welsh force's Cardiff Twitter account said: "Serious collision on M4 West between J32 & J33. Road Closed. Delays expected in both directions for several hours."