A sprinkler system has saved a Christchurch bedding factory from severe damage after a chemical explosion overnight.

The loss of Ashburton's historic Canterbury Flour Mill to fire this morning was a major blow to the regions's heritage, says the New Zealand Historic Places Trust (NZHPT).

Firefighters are battling a huge blaze at the historic Canterbury Flour Mill building in Ashburton.

A prisoner set fire to her cell bedding at Christchurch Women's Prison last night, causing extensive damage and injuring two prison guards who came to help her.

In a rare moment of unity, Australia's political leaders joined to mourn the victims of a catastrophic summer.

Bushfires that destroyed at least 59 Perth homes and forced hundreds of people to flee for their lives continued to burn last night.

A bushfire that tore across the outskirts of Perth over the weekend has destroyed at least 41 homes and damaged another 19, authorities said today.

Daylight in Western Australia has allowed helicopters back into the fight against bushfires still burning out of control in the Perth hills, where up to 40 properties have been destroyed.

More than 40 houses are expected to have been destroyed as a bushfire remained out of control in Western Australia.

Police have hailed two two passers-by as heroes after the pair, who were on their way to work, stopped and tried to save a man from a burning house in Christchurch.

Police made the "wrong call" to raise hopes for a rescue after the first Pike River Coal mine explosion, Grey District Mayor Tony Kokshoorn says.

A man has been hospitalised with burns and cuts after a caravan was deliberately set alight in Ashburton last night.

All 29 men lost in the Pike River disaster died within minutes of the first blast in the West Coast coal mine, a coronial inquest into the disaster has concluded.

The man charged with overseeing the Pike River mine smelled diesel or exhaust in the air about the time it was hit with an explosion that killed 29 men.

The 29 workers who died in the Pike River disaster would have died within minutes of the original explosion at the West Coast coal mine, a coronial hearing in Greymouth has heard.