This is in both directions.
Traffic Wales North & Mid put out a statement just after 8.30am on Monday, October 20.
They said: “Conwy Tunnel closed – both directions.
“Updates to be issued. Traffic will be diverted accordingly.”
It is understood the closure is linked to an electrical fault.
Janet Finch-Saunders, MS for Aberconwy, said: “The A55 Conwy Tunnel is a vital transport artery for North West Wales, so the traffic chaos caused with its closure is unsurprising.
“I have every confidence that the Traffic Wales team are using all the levers at their disposal to identify the cause of the problems and deliver a solution.
“We can all help them and all communities on the diversion route by only travelling if totally necessary.”
