The closure is an embarrassment for Whitehaven, which is seeking institutional and shareholder support for a proposed $5.1 billion scheme of arrangement with Nathan Tinkler’s Aston Resources.

NSW Department of Trade and Investment said it was made aware of poor safety practices and bullying of employees by mining supervisors and carried out an investigation of the mine.

Its investigation found several practices at the coal mine were unsafe and determined production should cease until they had been adequately addressed.

The unsafe practices included working over previously mined underground workings where there was a risk of collapse of the surface; unsafe entry to and exit from the truck parking area; working too close to loaded blasting holes; and inadequate lighting in the raw coal stockpile area and adjacent road intersection.

The inspectors also found there was unsatisfactory training and assessment of employees to operate plant and equipment at the mine.

Production ceased at 9.15am on Friday morning and the closure remained in force until the mine operator completed a full review of the safety management at the mine, which included full consultation with the workforce.

NSW resources and energy minister Chris Hartcher was informed and a detailed report was being prepared.

Whitehaven announced production resumed at Werris Creek after the suspension order was lifted at 8am this morning.

It said management and the workforce had reviewed a number of existing operating procedures and made a small number of adjustments.

Whitehaven open cut operations general manager Casper Dieben said the company’s overriding priority was to maintain the safety and wellbeing of its people.

“Concerns about health and safety are always taken extremely seriously,” he said.

“The Werris Creek mine has an excellent safety record and has operated for more than six years without any lost time injuries – we want to ensure this safety record is maintained.

“We have worked with the workforce since the suspension took place, to ensure everyone is satisfied with the procedures we have in place and that the workforce is aware of the safety requirements on site.

“A number of physical changes have been made on site, including an extension of the car parking area and improved lighting, as well as an amendment to pedestrian access and traffic flow at the haul truck parking area.”