Indonesia has declared its port city of Balikpapan to be in a state of emergency to stop the large oil spill from spreading off the coast of Borneo.

The fire, caused by spillage, had killed four people on Saturday. The spill had spread to an area of around 12km².

Disaster management officials are trying to control the impact of the spill.

The city’s environmental agency head Suryanto was quoted by Reuters as saying: “We have warned the public not to carry out activities that could spark fires.”

Balikpapan is home to an oil refinery operated by state-owned energy firm Pertamina.

Pertamina is probing where the oil had originated and clarified that its own underwater pipeline running in the area did not cause the leak.

“We will soon find out how big the impact is on the environment and who will be held responsible.”

The company’s external communications manager Arya Dwi Paramita was quoted by the news agency as saying: “At this time, our team is prioritising management (of the incident).”

The port city of Balikpapan has a population of 700,000. Residents are struggling to deal with the toxic smoke after the spill caught fire. Almost 1,200 residents living in the Penajam North Penajam Paser subdistrict reported complaints of nausea, vomiting and breathing problems and the city officials have distributed masks.

It is also suspected that the spill could have been caused by a bulk coal carrier, which was transporting coal from Indonesia to Malaysia.

Meanwhile, government officials have also gathered samples from Pertamina.

Indonesian Environment and Forestry Ministry director general Rasio Ridho Sani was quoted by The Guardian as saying: “Our team in the field is investigating it thoroughly.

“We will soon find out how big the impact is on the environment and who will be held responsible.”