More than 50 jobs are set to go from an iron ore mine in South Australia's Middleback Ranges near Whyalla, according to the CFMEU.
Western Australian based company BGC Contracting has told union officials the jobs will go and they will be switching off a digger and a number of dump trucks at the site.
CFMEU state secretary Aaron Cartledge said he was concerned some local workers might be replaced by a fly-in, fly-out workforce.
"We're trying to get to the detail of this. Our concerns at the moment are obviously with the local community and want to make sure there's preference given to local workers and not the fly-in, fly-out workers," he said.
The mine services the Whyalla steelworks, which has recently been taken over by British company Liberty House.
The company is owned by entrepreneur Sanjeev Gupta, who has promised to grow its operations.
Mr Cartledge said he was still waiting to hear why the jobs have been cut from the mine.
"We'd like to have further discussions with the new owners, with the Gupta family about taking directly on a number of those miners rather than using contractors," he said.
The ABC has contacted BGC Contracting for comment.
