Police are investigating the circumstances surrounding the death of a teenage boy after an incident at a Newcastle pool on Tuesday afternoon.

Key points: Police said the boy was restrained by several people at the pool

Police said the boy was restrained by several people at the pool Newcastle Council said he became unconscious, then went into cardiac arrest

Newcastle Council said he became unconscious, then went into cardiac arrest The 17-year-old was taken to John Hunter hospital, where he later died

Officers were called to the Lambton Swimming Pool about 5:00pm on Tuesday after receiving reports a boy had assaulted an employee.

A police statement said a number of witnesses restrained the teenager until Newcastle officers arrived.

The 17-year-old was treated by paramedics before being taken to John Hunter Hospital where he later died.

The teenager was at the pool with a carer.

Police tape surrounded an entrance to the pool last night. ( ABC News )

Newcastle Council owns the pool, but it is managed by private operators, Lane Four Aquatics.

The council's interim chief executive Jeremy Bath said the teenager became unconscious and then went into cardiac arrest.

"The 17-year-old boy, who was with a carer at the time became quite distressed, police were called to the pool, he became unconscious, went into cardiac arrest, he was taken to John Hunter Hospital where he sadly passed away," Mr Bath said.

He said the staff member assaulted was fine.

"It was a bit of push and shove, it was mostly verbal, with the staff member just trying to reassure the young man that he just that he needed to calm down," Mr Bath said.

"But unfortunately he didn't. He proceeded to start hitting a brick wall, and from there it ultimately ended tragically."

Critical incident investigation

Police said a critical incident investigation was underway to determine the circumstances surrounding the death.

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A police spokeswoman said police were not involved in the boy's death but it was procedure to launch a critical incident investigation.

That investigation will be subject to an independent review.

Police said they could not provide further details at this time but are appealing for witnesses to come forward.

The swimming pool posted a notice on their Facebook page on Tuesday night saying they would be closed due to "unforeseen circumstances".

The pool reopened on Wednesday morning.