Birds roosting on the roof of a leisure centre have been blamed for a warning not to swim on a Norfolk beach.
People have been ordered to stay out of the sea at Hunstanton due to poor water quality in the area.
Experts believe that droppings left by birds on the resort's leisure centre have washed into the sea, causing the pollution.
'No-swim' orders have been in force at Heacham, Hunstanton, Old Hunstanton and Wells in recent days.
They have now been lifted at Old Hunstanton and Wells, but remain in force at Hunstanton and Heacham.
For Hunstanton, the warning on the government's bathing water quality website says: "The Environment Agency is continuing to investigate surface water quality and identify any sources of poor quality water which may affect the bathing water.
"Due consideration is to be given to the potential impact of birds which roost on the leisure centre.
"Heavy rain falling on pavements and roads often flows into surface water drains or highway drains, ending up in local rivers and ultimately the sea. The quality of bathing water may be adversely affected as a result of such events."
The Environment Agency (EA) is also investigating the cause of 'faecal pollution' at Heacham, which it has previously said may be caused by bird droppings, livestock, dogs and human waste.
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Beach-goers were advised to stay out of the water all last summer.
Brown, foamy scum was seen over the weekend and on other occasions on the foreshore at Old Hunstanton.
The EA says: "A common marine algae found in UK coastal waters is phaeocystis, which is often mistaken for sewage as it forms foam and a brown scum, but it is non-toxic."
The EA has also said it suspects so-called misconnections, where toilets or waste water are allowed to discharged into storm drains rather than the sewerage system, could account for some pollution.
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