Multiple lorry crashes cause traffic problems
Pictures of the A31 lorry fire showed a plume of black smoke billowing into the air.
Hampshire & Isle of Wight Fire & Rescue Service (HIWFRS) said the trailer unit of the lorry, which was carrying "household waste", caught fire on the eastbound carriageway.
Crews from HIWFRS and Dorset & Wiltshire Fire Service attended and the contents of the vehicle were removed "to allow teams to continue damping down", a spokesperson said.
It is not known whether there were any injuries.
Hampshire & Isle of Wight Constabulary said there were no reported injuries in the Southampton Road incident.
There were "a number of people" with minor injuries but no-one seriously hurt following the crash near Ashley Health Roundabout, Dorset Police said.
Drivers are being advised to avoid the area.
The BBC has approached the ambulance service for more details.