A 13-year-old schoolboy with a severe allergy to dairy died after a cheese sandwich was allegedly stuffed or flicked into his mouth, pupils have said.

Karanbir Cheema, known as Karan, was taken to hospital last Wednesday (28 June) after suffering an allergic reaction at William Perkin Church of England High School in Greenford, west London.

The Year 8 pupil passed away with his parents by his hospital bedside on Sunday.

Police arrested another 13-year-old boy on the day of the incident. He was quizzed by murder detectives and has been bailed until later this month, pending an investigation.

One pupil tweeted on the day of the incident: "How can two idiots in my school stuff cheese down someone's throat — knowing that they're allergic to it, where's the logic."

Another student said: "A boy in the class bought himself a cheese sandwich and another boy asked to have a piece of it.

"He gave the cheese to him thinking that he would eat it but instead he flicked it at Karan.

"People are saying that it hit his lip, which he then licked by accident."

Alice Hudson, executive head teacher of the school, said that Karan had a "number of allergies" and that staff had managed to give him medication before the ambulance arrived.

She said the treatment had not been successful, however.

"Karanbir Cheema, known as Karan, was a popular Year 8 student at the school," she said.

"He had many friends who are devastated at his death, as are the staff. He was a bright and keen student who excelled in maths.

"Our thoughts and prayers are with Karan's family."

She added: "He was able to come to the school office to indicate that he thought he was having an extreme reaction and they were able to immediately administer the normal treatment, which was kept in the office for his care.

"Very, very tragically in this situation this was not effective."

The Met Police said an ambulance was called to the school just after 11.30am to a report of a pupil taken unwell after suffering a severe allergic reaction.

"The boy, aged 13, was taken to a west London hospital in a life-threatening condition," a statement said.

"Police were subsequently called when it became apparent that an incident had occurred which led to the boy coming into contact with the allergen. Those events remain under investigation."

A post-mortem examination is scheduled to take place on Wednesday.

Anyone with information that could assist the investigation is asked to contact police on 020 8785 8244 or contact Crimestoppers anonymously on 0800 555 111.