Officials trying to find what is causing the pollution on Norfolk's most noxious beach have been visiting nearby homes to see if they are leaking sewage into the sea.

Environment Agency (EA) officers have called on 90 properties in Heacham to find out if they are contributing to the chronic problems on the coast.

People are warned not to swim on the beach and the local water quality has been officially classified as 'poor' for the last four years.

Experts from the EA, as well as Anglian Water and local councils, have been trying to identify the sources of the pollution.

Eastern Daily Press: People have been warned not to swim at Heacham for the last two summersPeople have been warned not to swim at Heacham for the last two summers (Image: Chris Bishop)Anglian Water defends the role played by its nearby sewage treatment centre, which releases 'recycled' water into the Heacham river which then flows into the sea at the beach.

It says other sources are behind the poor water quality in the area, with seabirds - which are particularly numerous in this area of the Wash - accused of being the main culprit.

Another theory is that some homes and campsites in the area could be contributing, and it was to test this idea that the EA has been carrying out the checks, in recent days.

A spokesman said: “The pollution prevention visits were part of the Environment Agency’s joint action plan with the Borough Council of Kings Lynn and West Norfolk to investigate potential impacts on bathing water quality at Heacham. 

“Environment Officers visited approximately 90 homes in Heacham, checking for sewage issues and advising on septic tanks and general binding rules [which allow tanks to be used without permits]."

One minor issue was identified by the inspectors and fixed by the homeowner, suggesting the homes are not a significant contributor to the beach problems.

Investigations, including DNA testing, have so far failed to pinpoint the cause of bacterial pollution.

Eastern Daily Press: Sea birds are believed to cause some of the pollution off HeachamSea birds are believed to cause some of the pollution off Heacham (Image: Chris Bishop)

READ MORE: What is causing contamination at Norfolk's most noxious beach?

But officials say the local sea bird population is a "significant" factor, along with contributions from hooved animals like deer and cattle, as well as dogs and humans.

There are a large number of holiday chalets and caravans in the area, some of which are not collected to mains sewers.

The EA has previously said it is focusing its investigation on human factors and activities, including livestock farming.

There are also suggestions the changing shape of the Wash could also be a factor, as altered tidal movements and more sandbanks could be affecting the flow of water, causing less of the bacteria to be flushed out to sea.

Anglian Water insists its sewage treatment site is not responsible as its ultraviolet light disinfection system kills any remaining bacteria and viruses.