The restart of ventilation fans and removal of temporary seals last week, both approved by federal and state regulators, were successful.
"All six of the mine's ventilation fans are operating normally, and the underground atmosphere has been monitored for the past week to ensure that it was safe for the mine rescue teams to re-enter the mine," the company said.
The seals had initially been placed in November 2007 as a first step to re-entry into Buchanan. The regulatory requirement is to ensure an inert atmosphere underground.
The operation was evacuated and production suspended last July following a series of roof falls in mined-out sections that damaged a portion of the mine's ventilation controls.
The 5 million ton per annum metallurgical complex employs about 520 individuals.
