A Queendland boy came close to dying after swallowing a small battery.

An Australian expert was arriving in Greymouth tonight to provide advice on the jet engine GAG operation at the ill-fated Pike River Coal mine, where it's "highly likely" part of a coal seam has caught fire.

Wellington's Tranz Metro suspended all services in and out of the city bar one after a signals failure this evening, causing mass disruption at peak commuter time.

Another explosion shortly before 2pm today damaged some of the infrastructure at Pike River mine, but a "gagging" operation is still on track to commence tomorrow.

Ten arrests were made at the Christmas in the Park concert in Christchurch last night after a youth was stabbed and a police officer hospitalised.

"What gave armchair critics the right to criticise and worse - accuse the rescuers of deliberately sitting on their hands?"

A son has given evidence against his own father, accused of the murder of a mother of four.

"We pray that their moment of fear becomes eternal peace," said Monsignor Gerry O'Connor during an emotional tribute to the Pike River miners in Greymouth.