The contract extension is worth $190 million.
The scope of works includes the provision of a full range of underground mining services and equipment to support the mine's lateral development and associated ore production. That includes load and haul, shotcreting, cable bolting and full fleet maintenance services.
Cimic subsidiary Thiess began working at Leinster in 2016.
Its team excavated about 610m of horizontal development to access nearly 230,000t of ore using sub-level open stoping.
Thiess managing director Douglas Thompson said the Thiess team had a deep understanding of the mine and was well placed to help support its next phase of development and production.
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