The bomb squad robotic unit was transported to Mount Isa last week to help with the search, but Mount Isa Police Inspector Trevor Kidd said the team  never got to use it in the ore pass because the terrain proved too difficult, and the chute was too dark, for it to operate properly.

Last Friday police announced that the search for Mr Kelly was now a recovery mission after receiving advice about the worker's ability to survive underground since last Wednesday.

It is believed that Mr Kelly fell down an ore pass -  an underground shaft, roughly the same height as the Eiffel Tower, where up to 100,000 tonnes of loose ore from all levels of the mine is dumped to be crushed and conveyed to the surface at the lowest level of the mine.

Inspector Kidd said the time between Mr Kelly's disappearance on Wednesday and the ceasing of operations at the ore pass that afternoon was considered during discussions yesterday.

``We don't believe he's on top of the ore face,'' Inspector Kidd said.

``You can stand on the edge and check the top of the ore face but it's very difficult.

``You can't just get down there and start sifting through it, so you only have a visual, and pieces of this pass are constantly falling in and breaking off.

Inspector Kidd said it would take the recovery team some time to figure out how to safely search the ore pass.

``We've had further discussions and we're looking at the best options,'' he said.

``Yes, he [Brett Kelly] may be covered in some ore but there's a massive amount you would need to clear before we get to where he is.

``We'd obviously like to start as soon as we can, but we have to ensure we have plans in place so we don't risk anyone's safety.''

 A Mount Isa Mines spokeswoman said limited production at the underground copper operations  recommenced on Saturday.

``The area where Brett was last seen in our Enterprise Mine has been barricaded off while we continue to work with the relevant authorities as part of the investigation,'' the spokeswoman said.