Blue-green algae: Portstewart bathing ban until at least 11 July

Blue green algae can be harmful to humans and is highly toxic to animals.

A ban on bathing at Castlerock beach and Portstewart Strand will remain in place until at least 11 July.

The Northern Ireland Environment Agency (NIEA) said more testing would take place over the weekend to determine the extent of algal blooms in the area.

Potentially toxic blue-green algae was detected at the north coast beauty spots on Wednesday.

The beaches are red-flagged by the Royal National Lifeboat Institution, meaning it is unsafe to swim.

No-one should enter the water under any circumstances and dogs should be kept out of it as well.

Portstewart Strand is a popular swimming spot

Blue-green algal blooms have been detected at a number of sites across Northern Ireland during the recent good weather.

Suspected algae was reported to the NIEA at Castlerock Beach on 5 July by Department of Agriculture, Environment and Rural Affairs (Daera) samplers undertaking bathing water testing.

It was confirmed as likely to be a potentially toxic species.

Jenny O'Brien, who lives in Portstewart and works in Castlerock, told BBC News NI the blue-green algae warning was very concerning.

"It's very worrying from a business point of view as the summer season is very busy and we would be expecting a lot of visitors, but it's also very worrying from a health and safety point of view," she said.

"It's important nobody goes in the water when they shouldn't."

Ms O'Brien, who is a dog owner, said it was important that people were cautious when walking their dogs near beaches and rivers.

At the scene

Castlerock beach is all but deserted this afternoon, with bathers going elsewhere to swim.

Just a few walkers are strolling along the sand, in sunshine that should have brought hordes of people out for the day.

One woman's dogs danced along the edge of the water, before other beach visitors reminded her of the risks.

Castlerock beach was deserted on Friday

There have been no reported cases along these north coast beaches of people or dogs becoming ill after swimming here but elsewhere in Northern Ireland dogs are known to be affected after being in water where blooms of blue-green algae have been detected.

At the start of the holiday season, many traders here are bound to be anxious about the impact on business, with the ban set to last at least another four days.

Blue-green algae in Lough Neagh has been moving downstream with the natural flow of water for the last month.

It has travelled down the River Bann, reaching the coast.

Daera said the natural movement of the tides and wave action will break up the algae.

And it said that could mean some of it "potentially washing up on the shore".