Vitol has offered 45c for each Hillsborough share it does not already hold.

Vitol currently owns 24% of Hillsborough’s common shares and said it has inked a lock-up agreement with holders of another 7.1 million shares, or about 9% of the company’s remaining common shares.

"Our offer presents compelling value to Hillsborough's shareholders and creates an immediate opportunity for shareholders to receive cash proceeds for their investment," Vitol director Jacobus Sterken said.

Hillsborough has formed a special committee – made up of Michael Fitch, Barry Irvine and Emmet McGrath – to address the bid.

While Vitol and Hillsborough discussed a possible sale earlier this year, no deal came to fruition.

Vitol and Hillsborough already have a sales agreement for 44% of the producer’s output from the Quinsam coal operation through to 2012.

The supply deal was renegotiated earlier this month, with Hillsborough receiving about $US3.03 million in cash from Vitol and having about $16 million of its debt to the company cancelled. Vitol said it would continue to offer Hillsborough a $C6 million line of credit.

"Vitol Anker has decided to take its offer directly to Hillsborough shareholders to provide shareholders with an opportunity to benefit from an all-cash offer at a significant premium to Hillsborough's current market price," Vitol said.

Hillsborough says its independent committee will now oversee the preparation of a formal valuation of the company and it expects to respond to Vitol once that has been completed.

Hillsborough president David Slater told various local media that more would not be known for “at least two to three weeks” but confirmed his company had received the offer.

"At the end of last year we actually went through a whole valuation process. We just couldn't agree [on] value so we agreed to disagree and we thought actually that was the end of it, but clearly we were wrong," he said.