Mystery now surrounds the death of Hampstead schoolboy Joseph Benett after police this week revealed the canister he inhaled with friends did not contain laughing gas.

Joseph thought he was inhaling nitrous oxide, known as laughing gas, on the night of August 31 brought back from Israel.

But because the label was in Hebrew it would have been unclear what the canister contained, his family have told the Ham&High.

An initial post mortem result gave cause of death as a hypoxic brain injury and inhalation of nitrous oxide (N20).

But now police believe the canister may have contained other chemicals.

Inspector Ken Townsend, of Hertfordshire Police, said: “The canister did not contain nitrous oxide, however we are still awaiting a full scientific report and until we receive that report it would not be appropriate to make any further comment.

“The incident is an immense tragedy. There is currently no criminal investigation and the matter is in the hands of the coroner.”

An inquest into Joseph’s death was opened and adjourned at Hertfordshire Coroner’s Court Office after the teenager died on September 27.

Joseph’s sister Camille said: “There were two canisters which had Hebrew writing on them so it wasn’t something they could read. The boys all believed it was laughing gas and nothing else.

“We would like to take this opportunity to thank everyone who attended St Mary’s Church, for all the flowers, kind words and donations to St John’s Hospice.”