Police say bundles of cocaine washed up on a beach in Tan-y-Bwlch are worth about £42m.
A large number of black bags tied to plastic tubs were found by passers-by on Tan-y-Bwlch beach near Aberystwyth, Ceredigion, on 1 October.
More bundles were later found and all are thought to contain cocaine.
Dyfed-Powys Police said the haul weighed about 1,200kg and warned the public not to touch any more if it washed up, but to contact the force.
A statement said: “Forensic work continues on the substance found in the bags, but we believe it to be weighing approximately 1,200kg.
“This amount would have a wholesale value of approximately £42 million.
“Our investigation continues and we reiterate to the public that if they find anything suspicious on the beaches, the contents shouldn’t be touched and police should be contacted immediately.”
