Police are warning parents to be on the lookout for symptoms of a potentially deadly new craze among teenagers in Marlborough.

They are inhaling nitrous oxide, laughing gas, from small cylinders which can be bought on the Internet. Youngsters call it hippie crack, buzz bomb or whippets, and long-term use causes permanent brain damage because nitrous oxide starves the brain of oxygen.

Side effects to watch out for are dizziness, slurred speech and fits of the giggles. One St John’s School Year 11 boy discovered by PCSO Jon Mills using the gas appeared to be having a fit.

Possession of nitrous oxide by under 18s is illegal. Police warn that those caught with the three-inch metal cylinders it comes in will have it confiscated and could face the youth court.

Town council workers, who found large numbers of cylinders in Priory Gardens, Salisbury Road Rec and Elcot Lane playing fields, alerted PCSO Mills. Street cleaners found them in litter bins in St Mary’s Churchyard and on The Green.

The cylinders are used in the catering trade for whipping cream. They cost £140 for 600 and are used with machines that cost £15 on the Internet.

PCSO Mills believes someone is buying them in bulk and distributing them to teenagers. He said he came across eight children aged 14-16 in the Priory Gardens who had scores of empty mini-cylinders plus three boxes of full ones.

“I saw one lad inhaling from a balloon and it looked as if he was having a fit because his arms and legs were twitching.

“I want to make parents aware because I am sure that most of them do not know this is going in.”

St John’s headteacher, Dr Patrick Hazlewood, said: “We have found some of the canisters and located the people who brought them into school and dealt with them.”

He said anybody found pushing them faced immediate and permanent exclusion.

“If we become aware of any children using this or other substances, then we try to educate them out of this behaviour.”

A teenager who would not give her name said: “It’s everywhere, people are using it at discos and at all the festivals. At some festivals and raves they sell it from ‘gas bars’ where they have it in big cylinders and put it in balloons for you.”

Jennifer Kayne of the Government’s Medicines and Healthcare Products Regulatory Agency told the Gazette: “Administration of nitrous oxide without oxygen can be very dangerous. Hypoxia (oxygen starvation) can occur which may lead to loss of blood pressure, fainting and even heart attack,”

Parents who find any suspicious items should contact PCSO Mills 0845 408 7000.