Traffic is at a standstill after a lorry caught fire on the M4 Prince of Wales Bridge.
Thick smoke can be seen pouring from the lorry, which is carrying multiple pallets of wine, on the Second Severn Crossing.
Avon Fire and Rescue Service said noone has been injured.
In a series of tweets, the fire service said: "We are currently at the scene of a fire involving a lorry carrying 24 pallets of wine on the M4 Prince of Wales Bridge."
The statement continued: "The fire has now been extinguished. "Crews remain on the scene moving the cargo and ensuring the scene is safe."
Traffic monitoring service Inrix said at 3.21pm on Wednesday: "All traffic being temporarily held and queueing traffic due to vehicle fire on M4 Prince of Wales Bridge Westbound from J22 M49 to J23 M48."
Cameras show traffic has stopped on the bridge and large plumes of smoke can be seen around halfway across the bridge.
One woman stuck in traffic on the bridge said she has seen about six fire engines and a few police cars pass her. She said she can only see black smoke from the site of the incident.