Firefighters are praising a west Auckland woman who rushed into her neighbour's burning house and woke the sleeping occupants.

A massive fire broke out at a factory in the Auckland suburb of Penrose on Monday night.

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.