Further delays have been encountered by rescue workers trying to free the trapped miners in Beaconsfield Gold Mine in northern Tasmania, and it could be hours before they are released.
National Secretary of the Australian Workers Union, Bill Shorten, remains unwilling to speculate the time the rescue operation will be completed.
He says that the rock is proving to be a formidable obstacle, and drills are now being used because the jackhammers were ineffective.
"The rock that is being encountered is just a lot harder than expectations and the work is painstaking and could take many hours to come yet."
Mr Shorten also says the conditions that the rescuers are working in are cramped and the work is painstaking.
"You would have a miner kneeling, with one leg up. They would be changing their position all the time. You would have one man holding a drill, because it is the implement that is being used, which is an air drill and you would have one man behind the miner holding the drill to assist the first man."
Mr Shorten says that new options to remove the rock are being explored, including the possibility of drilling up to 50 small bores in the rock and then using explosives.