Jan 4 (Reuters) - Australian mining giant Fortescue on Thursday said a heat buckle in its railway line was behind the derailment of multiple iron-ore cars which cut the supply of the commodity to its Western Australia operations last Saturday.

The firm had on Wednesday said that multiple iron ore cars derailed at its Western Australia operations on Dec. 30, but signalled no impact on shipments for December or the first half of this year.

The company has opened an investigation into the cause of the heat buckle, especially as large parts of the country faced heatwave conditions. Local authorities have flagged a high bushfire risk in many parts of

Western Australia state

.

The wagons were empty when they derailed around 150 kilometres south of Port Hedland, Fortescue said, adding that no injuries occurred during the incident.

"Rail operations resumed on Wednesday as anticipated," a spokesperson for the miner said in an emailed statement to Reuters.

Miners around the world, including in Australia, have been taking precautionary measures to mitigate the risks of buckling as steel rail lines expand under extreme hot weather conditions.

Fortescue, which is targeting 192-197 million tonnes of shipments, including 5 million tonnes from its Iron Bridge magnetite project for fiscal 2024, kept its expectations unchanged despite the derailment. (Reporting by Rishav Chatterjee in Bengaluru; Editing by Dhanya Ann Thoppil)