South Wales Police says the A465 is closed between Aberdulais and Resolven, after a serious crash.
Diversions are in place via the B4242.
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After a mostly dry evening with a few scattered showers, cloud and outbreaks of showery rain will spread northeast through the night.
Tributes have been paid to former Wales international Mel Charles, who has died at the age of 81.
Tablets - of the computing variety - could help help patients and doctors in Wales as part of a technology revamp.