The latest flare-up was reported at Puncak 30 in Sumber district of Probolinggo regency, within the Bromo Tengger Semeru National Park, according to the Jakarta Globe, Anadolu Agency reported.
Oemar Sjarief, head of the Probolinggo Disaster Mitigation Agency, said a previously small hotspot expanded significantly on Monday morning, burning forest and surrounding vegetation.
Firefighting teams are conducting ground and aerial operations to contain the blaze and prevent it from spreading.
Three helicopters have been deployed for water-bombing operations, particularly over areas difficult for ground crews to reach because of the rugged terrain. Firefighters are also using water tankers and water-spraying drones.
Authorities said fires were still ongoing at two main locations on Monday, Puncak 30 in Probolinggo and Dengklek in Pasuruan regency.
Forestry Minister Raja Juli Antoni said water-bombing operations would continue until the blaze was completely extinguished, with a helicopter capable of making up to 30 drops a day when weather conditions permit.
Firefighters are also monitoring smoldering areas to prevent the flames from reigniting.