Rural communities south of Auckland are bracing themselves after news hundreds of steel mill jobs are at risk.

BlueScope is targeting $50 million in savings from its New Zealand operations, which includes Glenbrook at Waiuku, an iron sand mine at the mouth of the Waikato River, and a significant operation at Taharoa - south of Kawhia.

Franklin local board chair Andy Baker said while steel prices have been under pressure for some time, the news is a shock to the community.

"Unless you're really involved in the steel industry or aware of what the prices are doing, you haven't really put two and two together that there's the potential for some major impacts," he said.

"There's not many people that aren't connected some or another to the mill. This could have a pretty huge impact. It will have a massive impact if they can't do what they want to do."