Rescuers at the Greymouth mine in New Zealand say they are preparing for a possible loss of life.
Pike River Coal CEO Peter Whittall said they still do not know if it safe enough for rescuers to head down, while the option of a robot being used to facilitate any possible rescue still needed to be examined.
Drilling at the borehole was continuing to go well, and they hoped for a result on Monday night, Superintendent Gary Knowles said.
Knowles said gas analysis teams are still analysing samples to see if it was safe for rescuers to enter the mine once the drilling reached its target.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"We still remain optimisitic, we're still keeping an open mind but we are planning for all outcomes and this also includes... the possible loss of life as a result of what's occurred," Knowles told reporters.
They were continuing to test on a half hour basis, and were doing 'everything that is humanly possible', he said.
'We need to establish beyond reasonable doubt' that the operation was safe for rescuers, he said.
Equipment would include cameras and listening devices. The option of an army robot device which may be sent in was being examined still.
Whittall said he spent the morning with family members, showing them the activity at the mine.
Robot considered
He said there were some risks concerned with the robot, such as the dragging of cabling behind it, and so it must be properly assessed. The robot would also have to likely carry a range of equipment, while travelling some distance.
He said the drilling had got down to 135m so far, and they'd be switching drill types for the last section once they reached 150m, for safety reasons. Once the cavity was breached, he said he expected gas to come up the hole. This would allow for the collection of gas samples.
He said the condition of the miners could depend on where they are, but they would likely only have the lunch they took down with them on Friday.
Twenty nine men are trapped in the mine, and there has been no word since their disappearance following a methane explosion at the site on Friday afternoon.
