Staff working to seal the shaft of the Pike River Mine were evacuated from the site on Sunday, due to dangerously high gas levels.
Police say sealing cracks in the slimline shaft with a foam product will help to make the mine safe enough to enter by preventing the escape of neutralising gases being pumped inside.
Superintendent Gary Knowles says preparatory work was interrupted on Saturday and Sunday when dangerously high gas levels meant workers had to be evacuated.
Superintendent Knowles says the GAG machine, which helps to stabilise the mine gases, was shut down for maintenance on Saturday and returned to service on Monday.
Twenty-nine men who died in the mine after a series of explosions beginning on 19 November last year.
