Published: Nov 21, 2010 3:26 AM EST
Updated: Nov 21, 2010 12:26 AM EST

WELLINGTON, New Zealand (AP) - Rescuers are preparing to drill a gas sampling hole into a New Zealand coal mine where a powerful blast Friday trapped 29 workers.

The chief executive of the Pike River Mine says a six-inch-wide hole will be drilled 500 feet into the mine from the mountain above over the next 16 to 24 hours.

The hole will enable rescuers to sample gas levels from deep in the mine's center.
      
Underground combustion is continuing to generate dangerous gases, preventing rescuers from entering the mine.
      
Fresh air is still being pumped into the mine through an open air line.
      
Police say the miners, aged 17 to 62, are believed to be about 1.2 miles down the main tunnel.
      
Anguished relatives have been voicing frustration over the delays in the rescue operation.