The restart marked exactly a century since the mine first went into production.
Most mining firms rely on their own diesel supplies to extract iron ore, diamonds, rutile and bauxite in the resource-rich country.
Case centres on a 2018 toxic spill at the Badila oilfield, equivalent in volume to 34 Olympic-sized swimming pools.
The three executives, including CEO Terry Holohan, were freed from detention on Wednesday.
