More than 50 pupils have been struck down with suspected salmonella at a prestigious boys' school.

The pupils and a number of teaching and support staff at Worth School in Turners Hill, Crawley, were yesterday confirmed to be suffering from food poisoning.

In a statement, the independent boarding school said the most likely cause was salmonella.

It is unclear whether the infection originated inside the school or was introduced from outside.

On Tuesday, headteacher Peter Armstrong wrote to parents to say lessons would continue as normal but parents could keep their sons at home if they wished.

He said: "I am sorry to say the outbreak of food poisoning which we identified at the end of last week has not yet ended.

"As a precautionary measure I have decided it would be prudent to allow those boys whose parents wish them to return home to do so."

He said outside trips and visits were cancelled for the rest of the week.

Doctors from a nearby surgery have been involved since the initial outbreak, as has the Health Protection Agency (HPA) and the Environmental Health Department.

Mr Armstrong said: "We are taking all possible measures to protect the health of our students and staff."

Dr Kevin Carroll, a consultant in communicable disease at HPA, said they were working to identify the source of the outbreak.

"Every effort is being made to contain the spread of the infection."

Students and staff affected have filled out a questionnaire to help health professionals pinpoint the source and monitor the outbreak.

Salmonella is a bacteria usually found in poultry, eggs, unprocessed milk and in meat and water.

It attacks the stomach and intestines and causes sickness and diarrhoea, stomach cramps and fever.

Most infections clear up within four to seven days. More severe infections are treated with antibiotics.