The M4 motorway eastbound remains closed at junction 47 for Penllergaer while an overturned lorry is recovered from the carriageway.
Police are on the scene directing traffic, and a diversion is in place via the eastbound exit and entry slip roads.
The lorry contained a large quantity of frozen food, which is being removed from the carriageway.
Traffic is heavy on nearby roads, and long dealys are being reported.
A fire crew from Morriston station is also on the scene.