Four people have died while fighting wildfires on Indonesia’s Java island, as smoke from months-long blazes spreads across Southeast Asia, worsening air pollution and prompting Singapore to warn that it could take legal action against companies responsible.

The four victims died on Thursday while battling fires in Bromo Tengger Semeru National Park in East Java, Indonesia’s forestry ministry said in a statement. Two other people suffered serious burns and are receiving medical treatment.

The ministry described firefighting as a high-risk operation and said the safety of personnel remained a priority.

The fires have sent toxic haze across the region, forcing school closures in affected areas and raising concerns over public health, as several major Southeast Asian cities recorded elevated pollution levels.

Singapore Prime Minister Lawrence Wong said the city-state would pursue legal action against companies found responsible for the fires, including under legislation allowing it to target businesses whose overseas activities contribute to unhealthy air pollution in Singapore.

“Where warranted, we will take action under Singapore’s Transboundary Haze Pollution Act, and also explore joint action with other countries,” Wong said, without providing further details.

Singapore again topped IQAir’s live ranking of the world’s most polluted major cities on Friday, with Kuala Lumpur ranking second and Jakarta sixth.

The city-state’s air pollution index climbed to 251 at around 0400 GMT on Friday, placing it in the “very unhealthy” category under IQAir’s scale. Readings between 201 and 300 are classified as very unhealthy, while levels above 300 are considered hazardous.

“We cannot control the weather or the winds, nor can we directly control what happens beyond our borders,” Wong said.

“But we will do everything we can to protect Singaporeans, while working with our neighbours to address the underlying causes of the haze.”

Although Singapore has no major plantations or extensive forests of its own, several companies holding land concessions in Indonesia are reportedly based in the city-state.

Singapore enacted its Transboundary Haze Pollution Act in 2014 following a severe haze crisis in 2013. The legislation allows authorities to pursue companies whose activities abroad cause or contribute to unhealthy levels of air pollution in Singapore.

However, legal experts have warned that prosecuting companies linked to fires in neighbouring countries can be difficult, particularly when investigations depend on cooperation from foreign authorities.

Establishing responsibility requires evidence linking specific companies to fires, including satellite maps identifying hotspots. Overlapping land claims and disputes over concession boundaries can further complicate investigations.

Singapore’s investigations into four Indonesian companies over their alleged involvement in the 2015 haze crisis remain open. That episode severely strained relations between Singapore and Indonesia.

Other legal avenues, including a potential case before the International Court of Justice in The Hague, face significant obstacles because the court would need jurisdiction over the dispute, potentially requiring Indonesia’s consent.

Indonesia’s forestry ministry reported a significant increase in fire hotspots across six priority provinces, where authorities detected 615 hotspots.

A hotspot is an area where satellites register unusually high temperatures, potentially indicating a fire or another intense heat source. Not every hotspot necessarily represents an active wildfire.

Seasonal fires in Indonesia have repeatedly caused severe air pollution across Southeast Asia, with smoke affecting neighbouring countries and raising health concerns for millions of people.

The latest crisis has renewed calls for stronger regional cooperation, more effective fire prevention and greater accountability for companies whose land-management practices contribute to destructive fires.

Authorities continue to monitor the blazes and assess their impact as regional governments seek to contain the fires and limit further deterioration in air quality. (ILKHA)