Two more cases of E.coli have been confirmed in Orkney, bringing the total number of people with the infection to four.

NHS Orkney said the two new patients, who have the O157 strain, are recovering at home.

They were among three cases which were previously suspected. Two other patients are still being treated in hospital after they were confirmed as having the infection earlier this week.

One new suspected case has also been identified but no medical treatment has been required.

No link has been established between the four confirmed and two suspected cases.

Dr Louise Wilson, NHS Orkney's director of public health, said: "As I said this week, it is not uncommon that, after testing, other cases are confirmed. We are continuing to investigate these instances to look for links between the cases.

"I renew my encouragement to everyone to be scrupulous in their hygiene, including looking after the hygiene of others, such as children or adults in your care, as well as hygienic food handling and thorough cooking."

E.coli O157 is a bacterium which lives in the gut of animals such as cattle, sheep, deer and goats. It can also be carried by pets and wild birds.

In humans, the toxins that the O157 strain produces can cause diarrhoea and kidney failure as well as other illnesses. Young children and older people are said to be at the greatest risk.

Dr Wilson said: "On average, it takes three to four days for symptoms to develop after swallowing an infectious dose of E.coli O157. Symptoms can last up to two weeks, except in cases with complications.

"Most people get rid of the bacteria after about one week although children may continue to carry it for longer periods."