The M4 between Swindon and Chippenham remains partly closed after a fire involving a lorry carrying hay bales was reported more than 12 hours ago.
Traffic of more than three miles has built up this morning because only one lane has been reopened since police first reported the incident at 6.17pm yesterday.
The first and second lanes westbound between junctions 16 and 17 and the exit slip road at junction 17 remain closed.
Hundreds of vehicles stuck in tailbacks were released by 12.30am last night.
The fire is now out but the road is still being cleared up by National Highways and Wiltshire Police.
The services said they would reopen the road as soon as it was safe to do so.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here