Sea swimmers have been advised against bathing at a number of County Down beaches due to poor water quality.
The Department of Agriculture, Environment and Rural Affairs (Daera) said during routine monitoring, sites breached action levels for the bacteria Escherichia coli (E.Coli).
Warning signage is in place at the affected sites at Brompton, Ballyholme, Donaghadee and Crawfordsburn.
There was a sign at Helen’s Bay, but Daera said this was put up in error.
It added that heavy rainfall is known to impact water quality, and the Northern Ireland Environment Agency (NIEA) Emergency Pollution team is investigating the bathing water failures.
Northern Ireland had its wettest July on record, with figures going back to 1836, according to the Met Office.
Tests will be carried out on a further sample of water taken on Thursday, Daera confirmed, with an update on water quality along the north Down coast expected on Friday.
Ards and North Down Borough Council said it had been notified of the water quality failures at Ballyholme, Brompton and Donaghadee.
It said there had also been a failure at Crawfordsburn, an area which does not fall under council management,
“Signage has been erected advising members of the public not to swim in the affected areas and our environmental health section will review the situation and update signage after further water samples have been taken and analysed,” the council said.
It added that weekly results for bathing water quality were posted on the council website.
The warnings about water quality on some north Down beaches come during one of the most popular times of the year for swimming.
The water temperature rises throughout the summer and most beaches have hundreds of swimmers every day in August.
Most swimmers have heeded the warning not to go into the water at Bangor, Brompton, Crawfordsburn and Donaghadee.
On Thursday evening, the beaches were virtually deserted.
However, at Helen’s Bay swimmers were still going into the water.
Although situated next to Crawfordsburn, where swimming has been discouraged, there was a steady stream of bathers during the evening in Helen’s Bay.
Alliance North Down MLA Connie Egan said: “We’re so lucky in north Down to have the natural resources that we do, with so many beautiful beaches both locals and visitors alike make use of for activities like sea swimming, kayaking, and paddle boarding, among many others.
“It’s a real shame to see any of them out of action for any length of time, but for a number to be affected at once is very worrying indeed.”
Democratic Unionist Party (DUP) MLA Stephen Dunne said it was an alarming development and urged locals to take necessary precautions.
“Whilst the outcome is disappointing for regular sea swimmers and users, it is important that regular monitoring of water quality takes place in popular locations,” he added.