Hopes are dwindling for 29 men who remain trapped for four days after a mine explosion in New Zealand. Close circuit television pictures showing a powerful gas explosion which trapped the workers in a mine on Friday have been released by the rescue team. Police superintendent Gary Knowles told reporters it was still too dangerous for rescuers to enter the mine. He said the chances of finding anyone alive deep underground are diminishing. Meanwhile, the rescue efforts are continuing with vigour. A second robot is being brought in to replace the earlier one which broke down inside the mine. Knowles said rescuers were still assessing air quality in the mine in the country's south island, to decide whether rescuers can attempt to go in. A listening device is due to be lowered down a borehole, which is being drilled.