The miners union says hundreds of workers have been left unemployed a week before Christmas as central Queensland firm Bounty Mining Limited enters into voluntary administration.

Key points: Cook Colliery is being placed into care and maintenance by the receivers

Cook Colliery is being placed into care and maintenance by the receivers It is unclear how many workers are affected by the shutdown

It is unclear how many workers are affected by the shutdown Stephen Smyth from the CFMEU says the union will do all it can to support workers

Bounty took over the Cook Colliery near Blackwater in the Bowen Basin in 2017, following the collapse of the colliery's previous owner, Caledon Coal.

In an announcement to the Australian Stock Exchange (ASX), Bounty Mining said it had entered into voluntary administration with KordaMentha after a period of depressed coking coal prices and production shortfalls.

"It is the intention of the receivers to place the Cook Colliery's operations into care and maintenance whilst they undertake a review and develop a plan to sell the business and/or restructure the group," receivers PricewaterhouseCoopers said in a statement.

The drop in production came after a mining roof fall in October that buried the company's primary excavator.

Last month, the company told the ASX the collapse caused a direct fall in production of 23,000 tonnes and an indirect loss of 150,000 tonnes.

At the time, 21 workers were laid off.

The miners union is estimating up to 250 workers and contractors would be impacted by the latest shutdown.

The CFMEU said most of the remaining workforce was employed on a casual basis, meaning they have few entitlements.

'Disgraceful state of affairs'

CFMEU mining and energy Queensland president Stephen Smyth said workers at the mine had received little information about the owner going into voluntary administration.

"This is a disgraceful state of affairs," he said.

"Casualisation in our industry is out of control and it makes workers much more vulnerable, because they can simply be cut loose by the contracting firms at any time.

"The union will do everything we can to support workers affected by this sudden closure."

"We are trying to determine the total numbers as we speak," he said.

"It's terrible timing. These guys, if they were casually employed … their pay stops today.

"That means that they will actually be having to look for work prior to Christmas and they'll actually have a pretty bleak Christmas and New Year's."

He said some miners found out driving to work on the bus.

"We find it very ordinary, it's like getting a text message saying you're terminated.

"Certainly caught us by surprise, I actually found out about it on social media."

Mr Smyth said Cook Colliery has high-quality coking coal and has been shut down a few times before, but that he understood the wash plant would continue to operate.

He said much of the workforce had been contracted out to Emerald-based labour hire firm ABM.

The firm's director was unavailable for comment.