Wellington  - Hundreds of people at a school fundraiser and a wedding escaped when a series of explosions set off a massive blaze at a factory near Hamilton, on New Zealand's North Island, on Saturday, news reports said.

Firefighters alerted by an automatic alarm were caught in the flames when the explosions occurred as they entered the Icepak Coolstores factory in the suburb of Tamahere, about 10 kilometres south of the city.

Two fire trucks were reportedly set on fire and seven firemen were taken to Hamilton Hospital with injuries ranging from critical to moderate, authorities said.

About 80 people at a wedding party were evacuated and doctors and nurses at a nearby school rushed to help the injured, Radio New Zealand reported.

The hospital said it had received mass casualties and issued a public appeal for the injured to be taken to other medical centres because emergency staff could not cope, reports said.

The TV3 channel showed footage of a huge blaze said to be out of control, and local residents said a plume of smoke rose two kilometres into the sky.

There was no immediate word on the cause of the blaze. Factory chiefs said that no staff were in the building at the time. (dpa)