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(CNN) -- The fate of 29 New Zealand coal miners and contractors remains a mystery more than 20 hours since they were last above ground, with rescuers awaiting word that conditions are safe to go after the trapped men.
An explosion rocked the Pike River mine, on New Zealand's west coast between Greymouth and Reefton, around 4 p.m. Friday New Zealand time. Two men walked out with minor injuries, but their colleagues -- ages 17 to 62 -- were trapped as much as 2.2 kilometers (1.4 miles) from the tunnel's opening and have not been heard from since.
For now, authorities are monitoring results from a series of tests to determine if the air-quality underground is safe enough to send in help. The four tests conducted thus far, focusing on carbon monoxide levels, have been "inconclusive," said Pike River Coal CEO Peter Whittall at a Saturday afternoon press conference.
The rescuers are miners themselves, according to Gary Knowles, superintendent of the Tasman Police District, who is heading the rescue effort. For now, they are conducting drills and ready to go in at a moment's notice.
"Safety is paramount for me," said Knowles. "When the opportunity arises, they'll be ready to go. They want to save their colleagues."
The miners' families, meanwhile, are at a Red Cross hall in Greymouth, about an hour from the site, where they're getting updates from the mine company and emergency rescue personnel.
Whittall said the relatives are away from the mine site, near the town of Atarau about 90 miles northwest of Christchurch, because "it doesn't add any value to the rescue operation and it doesn't add value to them, either." Right now, they are mostly left to wait.
"There's 29 men down there. And there's 29 families. And there's 29 different sets of circumstances," said Whittall. "And all of them are dealing with it in their own way."
The two survivors, one of whom has a brother trapped underground and whose father is the mine's safety manager, spent Friday night in a local hospital after suffering moderate blast injuries before being released Saturday. They both have talked to authorities, who still don't know what caused the explosion or the current condition of the mine.
There are drinking water sources underground, said Whittall, and the workers likely brought some food with them. Although no contact has been made, officials are hopeful the trapped men found refuge near a ventilation shaft and might be getting fresh air from a broken compressor pipe.
The situation in New Zealand is different from Chile, where rescuers successfully freed 33 men stuck underground in a copper and gold mine for 69 days. There are two routes out of the mine, Whittall said. Unlike the Chilean mine, where 33 miners were rescued in mid-October, the Pike River mine has steep terrain, and the shafts run horizontally into the hill, not vertically into the ground.
"This is not Chile. It's a whole different type of mine," said Knowles.
Still, like in Chile, government and rescue authorities said they've been getting offers of help from around the region and the world. Gas testing equipment has been flown in from Australia to help with the rescue operation, with engineering and health experts ready to assist. A Facebook page devoted to the rescue effort had attracted over 9,500 supporters by Saturday afternoon from people wishing the miners well, offering prayers and asking for information.
New Zealand Prime Minister John Key, who spoke briefly at the end of Saturday's press conference, said that he's received offers of help from many groups and people, including an e-mail from Prince William that his heart went out to the miners.
"From the government's perspective, we're doing everything we can to make sure these 29 brave men are taken out of the mine," said Key. "It's a difficult time for everyone."