Seven hurt in school explosion

A high school explosion which shattered windows and sent metal objects flying across the classroom has left six students and their teacher injured, some seriously.

Four of the injured students were last night in Whangarei and Auckland City Hospitals following yesterday's blast, which occurred while 18 students were in an engineering class at Kaitaia College.

At least two of the students were understood to be in a critical condition last night after being thrown across the classroom.

Residents and businesses up to a kilometre from the school reported hearing a loud bang about 1pm.

Brenda Johnson, who lives about 30m away, was in her lounge when she heard the explosion, which may have been caused by a leaking oxy-acetylene cylinder.

"All of a sudden ... I heard this boom and thought, 'What the hell is that?' I looked out the window and saw some kids running out of the classroom."

Mrs Johnson said there was no sign of smoke or flames but the classroom windows were shattered.

The fire alarm went off and students and teachers gathered on the field, where the principal used a loud-hailer to explain what to do.

Mrs Johnson said staff from a nearby clinic came running to the college carrying medical equipment but she could not see if the students who fled the classroom were injured.

The six Year 11 students and the injured teacher, believed to be in his 40s, were taken to Kaitaia Hospital, and four were transferred by the Westpac and Northland Electricity rescue helicopters to Whangarei and Auckland City Hospitals.

They are thought to have suffered head and facial injuries, including cuts from the flying debris and possible ear damage from the sound of the explosion.

Senior Sergeant Gordon Gunn of Kaitaia said leaking gas from a welding cylinder was being investigated as one possible reason for the explosion, which caused widespread damage to the classroom.

"It shattered ... about 70 per cent of the windows and caused some damage to the rear of the classroom," Mr Gunn said.

Metalwork equipment, tin cutters, wood and panelling had been hurled the length of the classroom before embedding in a wall.

Other items were flung towards the windows and doors, shattering wire-mesh safety glass.

Mr Gunn said the explosion did not appear to be malicious so the police would wind down their involvement while Occupational Safety and Health and Fire Safety staff took over the investigation.

"I'm really quite grateful that there weren't more children seriously more injured ... or killed," Mr Gunn said.

Volunteer fire support officer Colin Kitchen said the explosion was a "pretty traumatic" experience for everyone involved, especially those in the classroom, which "resembled a war zone".

"There were a lot of flying objects and things embedded in the walls. It was not a good sight."

A statement from the college said the parents of the injured students had been contacted straight away.

Victim Support travelled to the school to offer help to other students and staff members.

The Ministry of Education had also offered support for staff and students.