A kitchen worker at a public school in Buckingham has been arrested over claims soup was poisoned.
Stowe School contacted police last week and a 58-year-old man from Brackley, in Northamptonshire, was arrested.
Staff became suspicious after noticing a chemical smell in the carrot and coriander soup, but no-one fell ill.
The porter was arrested at his home on suspicion of administering poison with intent to endanger life and released on bail until March 29.
The school, which has 750 pupils aged between 13 and 18, said an email was sent to parents on Tuesday telling them of the arrest on March 12..
Head teacher Dr Anthony Wallersteiner said: "I would like to reassure parents that no pupils or members of staff were affected in the incident."
The police said they could not detain the porter for health reasons.
Det Con Vicky Ball, of Thames Valley Police, said: "Nobody has been harmed, but these are serious accusations.
"Our investigation is still in its early stages and forensic work is continuing."
Staff were carrying out routine checks before food was served to the pupils when they became suspicious that the soup had been tampered with.
The school, established in 1923, said 90 percent of its pupils are boarders, with about 70 day pupils from the area.
