Hampshire County Council’s traffic monitoring service has reported the vehicle fire blocked several eastbound lanes of the busy road between junction 12 near Port Solent and the A27 near Portsbridge Roundabout, in Hilsea almost an hour ago.
Now lane two of the eastbound road has been cleared, but lane one remains blocked, causing 30 minute delays from junction 11 near Fareham.
The National Highways South East Twitter account said that traffic had been diverted at junction 12 near Hilsea before lane two of the road was reopened.
The tweet continued: ‘There is approx. 3 miles of congestion which is likely to add around 20 minutes to normal journey times.’
Emergency services have been contacted for further information.