Police said in October about 19 staff were working on the case.
Police said yesterday they had undertaken an initial high-level feasibility study to investigate the need for additional boreholes at the mine site to support the ongoing investigation.
They did not say exactly what they were hoping to see.
"The feasibility study looked at the logistics of drilling additional boreholes from an operational, health and safety and cost perspective alongside any potential benefits to the investigation.
"Following the initial work on a feasibility study police will now undertake further work on more detailed projections in regard to timeline, cost and other requirements," a police representative said.
The study was led by police with support from the Pike River Recovery Agency and specialist geotechnical advice.
Should a decision ultimately be taken to drill additional boreholes, this would be part of the ongoing police investigation.
"New Zealand Police is committed to undertaking a full and thorough investigation at the mine site to ensure we do everything we can to provide answers as to what occurred on November 19, 2010."
Police did not say if they had an estimated cost. However, the agency’s separate budget is $51million.
The agency said in its newly released annual report that if the drilling went ahead it was "likely to affect the timeframe for completion of the project".
