Cilacap. Thick black smoke billowed from state-owned oil and gas company Pertamina’s refinery in Cilacap, Central Java, on Thursday morning, raising concerns among residents. The smoke, visible from a two-kilometer radius, was first noticed around 9:30 a.m.

A local shop owner near the site said residents and refinery personnel immediately rushed toward the source. Security officers were also seen heading to the area, but no flames were visible.

By late afternoon, the smoke was still apparent, but the cause remained unclear. Despite the incident, the surrounding area remained calm, with residents going about their daily activities and traffic operating as usual.

In response to circulating reports, Kilang Pertamina Internasional RU IV Cilacap denied claims of an explosion or large-scale fire at the refinery. Acting Area Manager for Communication, Relations, and CSR, Sunaryo Adi Putra, clarified that the affected tank, 38T-101, was undergoing routine sludge cleaning as part of scheduled maintenance.

The smoke appeared during the cleaning process around 11:00 a.m. due to a brief flash fire. Pertamina’s firefighting team quickly controlled the situation, and the tank is now in the cooling phase.

“Foam has been applied, and cooling is in progress. We confirm that there were no casualties,” Sunaryo said.

He said the tank contained no fuel, only residual sludge, eliminating the risk of a major fire.