A milk tanker that was travelling Westbound on the M4 has overturned near junction 18.
Avon and Somerset police received calls at 6:20am that the tanker was blocking all three lanes.
The driver suffered minor injuries and one girl was taken to Bristol Children's Hospital but her injuries are not thought to be life threatening.
All motorists stuck behind the incident have been diverted off the motorway.
Milk and diesel has been spilling onto the motorway which will now mean the road may need to be resurfaced.
The M4 Westbound is expected to be closed until the afternoon.
A police investigation is underway.