>> 36 miners missing after New Zealand explosion

Authorities hoped to send a rescue crew inside the Pike River coal mine "within the hour" in the afternoon of November 20 after three of four air quality tests showed improvement, local reporter said. 

The men, ages 17 to 62, were trapped in the mine after an explosion around 4 PM on November 19 (New Zealand time), and have not been heard from since. 

Authorities have delayed rescue efforts until they could be sure the atmosphere inside the mine is safe. Gas testing equipment has been flown in from Australia to help with the rescue operation.

Although no contact has been made, officials remain hopeful the trapped men found refuge near a ventilation shaft and may be getting fresh air from a broken compressor pipe. 

Emergency crews have interviewed the two miners, trying to determine what happened, but they were unable to pinpoint a cause, officials said. The miners had moderate blast injuries, with one being treated in the emergency room and the other in a ward of a hospital. Both were up, "walking and talking", police said.