South Wales Police says the A465 is closed between Aberdulais and Resolven, after a serious crash.
Diversions are in place via the B4242.
More top news
Another windy day with some heavy showers especially in the north. Some decent spells of sunshine in many places but feeling chilly.
Plaid Cymru leader Leanne Wood launches party's election manifesto saying it wants a better funding deal for Wales and an "end austerity".
Brit Award winner James Bay is among the next wave of acts announced for the festival in September.