Viva Energy Group Ltd's stock plummeted 9.09% during intraday trading on Monday, as investors reacted to news of a fire at the company's Geelong refinery that has significantly reduced production capacity.

The fire, which occurred on April 15 at Australia's largest refinery, has forced the facility to operate at reduced capacity. The company expects the Geelong refinery to produce diesel and jet fuel at approximately 80% of capacity and petrol at around 60% in the short term. The residue catalytic cracking unit remains offline while operations are stabilized, though the company aims to restart it and lift production to over 90% of capacity within weeks.

The incident comes at a sensitive time for Australia's fuel security, with the Middle East conflict already disrupting global supply chains. While Viva Energy reported a strong first-quarter refining margin of US$22.0 per barrel and has sufficient fuel stocks to maintain normal supply to customers, the production disruption at its key refinery has raised concerns among investors about near-term operational performance.