Racist symbols have been drawn on the Cofiwch Dryweryn mural between Aberystwyth and Llanrhystyd.
A swastika and a circular symbol associated with white power groups have been scrawled on the red-brick mural in what appears to be black spray paint.
The famous Welsh landmark, which sits on the side of the A487, was painted in memory of the village Capel Celyn.
The Welsh village was intentionally flooded in 1965 to make up part of a reservoir of water that supplies Liverpool and the surrounding area.
It is thought that the memorial was first painted in the same decade.
Dyfed-Powys have confirmed they are investigating the incident.
A spokesperson for the force said: “Aberystwyth Police is investigating an offence of criminal damage to the Cofiwch Dryweryn memorial on the A487 near Llanrhystud, which was reported at 11.30am this morning, Tuesday, 30th June 2020.
“Officers have attended the scene and enquiries are continuing.
“Anyone with information that could help officers with their investigation is asked to report it to Dyfed-Powys Police, either online at: http://bit.ly/DPPReportOnline, by email at: firstname.lastname@example.org, or by calling 101.
“If you are deaf, hard of hearing, or speech impaired text the non-emergency number on 07811 311 908. Quote reference: 126 of the 30th June.”
Multiple acts of vandalism
This is not the first time the wall has been attacked.
Multiple acts of vandalism have been carried out on the piece, including in 2014, and twice in 2019 – with hooligans even destroying the topmost part of the wall at one point.
The mural has been rebuilt or painted every time, however.
Cllr Elin Jones is one of many people to have already called out the most recent act of vandalism, describing the racist symbols as “sinister and dangerous”.
“Police are aware of the swastika on the Cofiwch Dryweryn wall,” Cllr Jones said.
“If you have information, tell the police.
“This is not a prank – it is sinister and dangerous.”
Y swastika wedi ei pheintio ar Wal Tryweryn. Afiach. Mae’r heddlu yn ymwybodol ac yn edrych mewn i’r mater.
Police are aware of the swastika on the Cofiwch Dryweryn wall. If you have information, tell the police. This is not a prank – it is sinister and dangerous. pic.twitter.com/EKtWxKgQ4u
— Elin Jones (@ElinCeredigion) June 30, 2020