Red flags have been raised on seven beaches in Valencia, eastern Spain, banning people from entering the water. The alert has been issued after a mysterious substance appeared in the sand.

The Guardia Civil’s environment unit, Seprona, is investigating what the material is and where its come from. The speckled white substance started to appear during the weekend over several miles of coastline in the Safor region of Valencia. Currently, red flags have been raised at beaches in Guardamar de la Safor, Gandia, Piles, Oliva, Miramur, Daimus, and Bellreguard – hotspots popular with tourists, many from the UK, at this time of year.

Photos posted by the local authority showed long lines of small white particles, seemingly washed ashore by the tide, that appeared to be roughly the size of grains of rice. They appeared similar in size to the small pellets of plastics that are shipped worldwide to manufacture household and industrial products. However, Spanish authorities have did not immediately given any indication as to what they believed the material might be.

Gandia’s restrictions are precautionary in an area around 500 feet north of the breakwater and also on Marennys de Rafalcaid beach, according to The Olive Press. Closures in the affected areas started being implemented on Monday morning.

The Valencia Port Authority has also been informed by the Maritime Captaincy with the substance being detected in port waters with the highest concentration towards the mouth of the Serpis river, which flows into the Mediterranean at Gandia, just north of the affected beaches.

The Maritime Captaincy is continuing to monitor the area through the Maritime Rescue team to detect any new areas that might be affected.

This will come as worrying news to Brits, who flock to the coast of Valencia each year. In 2024, an estimated 2.4 million British tourists visited Valencia. This number was a significant 11.3% increase compared to the previous year, making the UK the leading source market for tourists to Valencia, according to javeamigos.com.

This latest closure comes just days after a popular beach in Lanzarote, in the Canary Islands, was forced to close after a shocking public health warning. The public have been urged to stay out of the waters on Playa Dorada after tests revealed microbiological contamination. Taiza Town Council imposed the temporary ban on swimming on Tuesday after water samples came back positive for signs of pollution. 

The beach will only reopen once tests confirm the water is safe for swimming.