An explosion occurred at the Pike River Coal mine on New Zealand South Island's West Coast on Friday afternoon, with up to 36 miners unaccounted for, police and media reports said, Xinhua reported.
The incident happened at 4.30 p.m. (03: 30 GMT) in Atarau, which is 50 km northeast of the West Coast town of Greymouth.
A mix of miners and management, who were on a safety tour of the mine when the blast occurred, were among those missing.
Pike River Coal CEO Peter Whittall confirmed those affected were a mix of afternoon shift workers and management.
He said emergency services were on stand-by at the mine entrance.
There were six ambulances and three rescue helicopters from Nelson, Greymouth and Christchurch at the scene.
Two miners have emerged from a service portal in a separate part of the mine, and are being interviewed by mine managers and emergency services.
Police said they will not know any detail until officers and ambulance staff arrive at the scene.
Energy Minister Gerry Brownlee said mine officials had no idea what caused the blast, or the condition of the miners who were trapped.
The Brunner seam at Pike River holds the largest-known deposit of hard coking coal in New Zealand, with 58.5 million tonnes of coal in-ground. It runs six km north-south and up to one-half km east-west, averaging about 7 meters in thickness.
The company had recently almost halved its production forecasts for the 2011 year to between 320,000 and 360,000 tonnes.