People have been warned not to swim at one of Northern Ireland’s best-known bathing sites after a “significant” amount of blue-green algae scum was detected in the water and also on the beach.

Stormont’s Department of Agriculture, Environment and Rural Affairs (Daera) said the scum detected at Portstewart Strand on Monday posed “potential health risks”.

It has advised the public not to enter the water and to keep pets “at a safe distance” from any scum on the beach.

Exposure to high levels of any blue-green algae blooms can cause illness in humans but it can also result in the death of animals.

The presence of blue-green algae in Northern Ireland’s waterways has posed a significant problem in recent years.

In a statement, Daera said the latest detection was made following routine sampling at Portstewart on Monday.

The strand is managed by the National Trust.

Daera said it advised the trust to issue an “advice against bathing” notice at the County Londonderry beach until further notice.