And officials are warning people to stay out of the water and make sure their pets don't go in.


Blue-green algae made its unwelcome annual appearance at Pennington Flash earlier in the summer but fears have grown that this year's poisonous blooms are even larger than usual.


Warm weather during the past week is expected to make the problem worse over the coming days and it has prompted Wigan Council's Environment Agency to issue a further warning urging people not to swim in the water.


Peter Alker, park ranger at Pennington Flash, said: "Our bloom of algae is quite bad compared to the last few years and may get even worse in this warm weather. We want to remind people to stay out of the water and to keep their pets out of it too.
"Water is such an attraction in hot weather and it is particularly worrying when children are off school.
"Permanent warning signs are up at key points but we are keen to get the message across, especially during the school holidays."


Blue-green algae is found naturally in inland waterways while lakes and ponds plus warmer summer weather provide ideal conditions for its growth.
The algae rises to the surface of the water as a scum and looks like blue-green paint.


Eye irritation, vomiting, diarrhoea, skin rashes, muscular pains and fever have occurred in people who have swallowed or been swimming in infected water. The algae can be particularly harmful to animals.
Levels of the algae fluctuate, dispersing in the wind one day but coming back at any time depending on the weather.


Martin Kimber, Wigan Council's director of environmental services, said: "The flashes are popular places, but contact with the algae should be avoided. People should not swim in the water and should keep their pets well away from it."