Islanders are being advised against swimming at Grève de Lecq after water samples showed high levels of E.coli.
Signs are being put up on the beach advising against bathing.
Anyone who has been in the sea there and starts to feel unwell should speak to their doctor.
The bacteria, which can cause diarrhoea, stomach cramps and fever, was discovered in a sample taken near Grève de Lecq this week. It returned a count of 3300 cfu/100ml, which officials say is 'considerably higher than the European threshold for “poor” water quality'.
The testing was part of the government's routine monitoring of bathing water qualityat 16 bays between May and September.
The Pollution Control team is investigating the cause if the high E.coli levels.
Jersey declares Storm Goretti a major incident
Sanctioned Russian tanker sailing north of Channel Islands
CI Airports to close early as Storm Goretti approaches
Gorey Hill faces 10 weeks of electricity network upgrades
Man jailed for smuggling cocaine in Kinder eggs
Storm Goretti prompts stay-at-home warning in the Channel Islands
Islanders warned to stay inside during Storm Goretti
Little islanders now offered free chickenpox vaccine
