Three rapid response vehicles and five emergency ambulances were sent to the scene, where there were "multiple casualties", a spokeswoman for Welsh Ambulance Services NHS Trust said.
She added the ambulance service was called to the single vehicle collision at about 8.55am this morning.
More top news
Having now heard Theresa May's Florence speech, I have a bit more understanding why Boris Johnson cut up rough last weekend.
As Theresa May unveils plans for a two-year transition period, and Nigel Farage says she's 'betrayed' Leave fans...what do voters think?
A milder night ahead with patchy rain in the south giving a soggy and slow start to Saturday in places.