The A465 between Glynneath and Hirwaun has now reopened, South Wales Police say.
One person was taken to hospital earlier in the evening after 12 vehicles were involved in a collision.
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Rain clipping the far north through the evening but elsewhere staying dry with some sunny spells.
Public Health Wales figures show 25 more cases of the virus have also been confirmed.
Photos taken on Saturday morning show Roald Dahl Plass strewn with empty beer bottles and discarded canisters of laughing gas.