People are being warned not to go in the water near Lowestoft's south beach after worries over pollution were raised by lifeguards.
The 400m stretch of the beach which the RNLI lifeguards cover is currently under red flags, the sign that means to stay out of the water as swimming is unsafe.
The flags were initially raised on Saturday and have been up since, meaning the beach was deemed unsafe for swimmers for the entirety of the bank holiday weekend.
The Coastguard were also called out to the beach and contacted the Environment Agency on the same day.
It is undestood lifeguards saw black spots on the sand on Saturday and raised the possibility of pollution with the Environment Agency who visited the beach over the weekend and took samples.
It is not known where the source of the potential pollution is, nor what may have caused the pollution to enter the water.
A spokesman for the lifeguards said: 'We feel that the water quality is not good enough to have our red and yellow flags up.
'Therefore until we hear the all clear from the Environment Agency we will be having our red flags up because we want everybody to be staying safe.
'If red flags are up, don't go in the water.'
Waveney District Council, who are responsible for whether the beach stays open, said they had visited the beach.
They said environmental health officers had inspected the water and came to the conclusion there was no presence of any materials which pose a health risk, therefore meaning a closure was not required.
A spokesman from the Environment Agency said: 'We received a report on Saturday, 25 August, of a brown, oily material in the sea just off the beach at Lowestoft.
'An Environment Agency officer took a sample on Sunday, 26 August, and this is being sent to a laboratory for analysis.
They added: 'An officer will be in Lowestoft later today to undertake an inspection and to carry out further sampling if necessary.
'For information about the bathing water quality please contact Suffolk Coastal and Waveney District Council.'
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