( 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 does n't add any value to the rescue operation and it does n'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 do n'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 . ''
Rescuers are waiting on air-quality safety tests to go after trapped miners . The mine is located in the northern part of China's Shanxi province and has been closed since last year due to a lack of funds for maintenance. Authorities have met with family members of 29 trapped men . Those trapped could be as far as 2.2 km ( 1.4 miles ) from the mine entrance .