Dave Webb, president of Tyhee Developments, said work got underway April 4 and the crew is extending drifts, which run parallel to the gold strike and extending the declining ramp.
The work is designed to extend the gradually declining ramp, which is 600 metres in length but only 75m below surface, Webb said.
"We need to get more information. The zone is about a kilometre long and we've drill tested to 450m below surface," said Webb.
Fuel, equipment and bulk supplies sufficient for all work planned in 2005 have been trucked to the property over the past three months.
Underground mining consists of extending the drift on the first level (280 metres) to the south for an additional 75 metres.
The main ramp will be extended an additional 75 metres to the north before turning to the south.
Diamond drilling will commence from the main ramp in the Ormsby Zone, providing further definition of the existing gold zones and identifying new zones.
"It's much like a parking garage," said Webb while explaining the degree of descent of the tunnel.
Tyhee still has a lot of untested ground to cover, said Webb.
The current project should take Tyhee through to November or December. The plan is to shut down before Christmas.
If the Yellowknife Gold Project is to become a mine, the ramp would eventually have to go down much further, Webb said.
"We're trying to take it down and open up as much as we can for a pre-feasibility study, leading to a full feasibility study. That's the document we will take to the banks to see if they can provide financing," said Webb.
"All we're doing is minimizing the risk. They will ask: Are you sure this resource is down there? Are you sure you can extract 'X' amount of resources? (They're) simply questions they need to ask to provide us with the dollars we need to advance. It's really all about removing the risk that a risk-adverse group would want."
The Yellowknife Gold Project consists of 6,625 hectares (15,481 acres) of mining leases.
The property hosts several areas of gold mineralization, including the partially developed Nicholas Lake Gold Deposit, the Ormsby Zone and the West Zone.
Resources total 1,049,000 ounces of measured and indicated gold grading 9.01 grams per tonne.