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.

Police have launched an international search to find the husband of a woman burned to death by the side of a Waikato road last week, after he flew to Fiji with their four-year-old son the day after her body was found.

The husband of a woman found burned to death next to a Huntly road last week fled overseas with the couple's four-year-old son the day after her body was found, say police.

Police have identified the woman found burned to death next to a Huntly road and say her husband - who left NZ with their son on Friday - is a person of 'considerable interest' to their investigation.

A woman whose body was found burning by a remote Waikato road was alive when she was set on fire.

Police believe they have identified a woman found on fire on Thursday evening, and that an accelerant was used to start the blaze.

Police are tonight still trying to identify a woman whose burning body was on the side of the road in Waikato overnight.

Police are appealing for help identifying the body of a young woman found on fire near Huntly last night.