The A469 Brithdir, just north of the Deri (‘Puzzle House’) junction, is currently closed in both directions due to a water mains leak.
Motorists can still continue their journey along the A4049 between New Tredegar and Bargoed, although some delays can be expected.
A spokesman for Caerphilly County Borough Council said: “The duration of the closure is unknown at present and we will provide a further update when more information becomes available.”