Rescue efforts have begun in Indonesia following the burning of a passenger ferry off Madura Island that killed 28 people and has left another 28 missing, authorities said Monday.

On Sunday, the KM Mutiara Sentosa ferry, which carried 271 passengers, was en route from Surabaya in East Java to Makassar in South Sulawesi, when the fire erupted. Madura Island is an island off the north-east coast of Java Island.

Director of Marine and Air Affairs of East Java Police Arman Asmara Syarifuddin said that 238 passengers have been rescued and five have been confirmed dead, while they are still searching for the rest of the passengers who were still missing on board the plane.

Authorities are conducting a massive search operation with the help of the National Search and Rescue Agency (Basarnas), the police force and the Navy. Seven rescue boats (a naval corvette, patrol and speed boats) and one helicopter have been dispatched for the operations.

Search parties are searching 10 miles East and West of the accident. The operation will last for seven days, and will extend for a further 14 days if necessary, officials said.

The cause of the fire remains a mystery and investigations continue.

On Monday morning, all rescued passengers were successfully taken off, going to Gapura Surya Nusantara Port in Surabaya where they were provided with medical and other aid services.

With over 17,000 islands, Indonesia heavily depends on ferry transportation as a travel mode. While the incidents on land occur relatively infrequently, the maritime experiences a considerable share of accidents – caused by overcrowding, unanticipated weather conditions, and differences in safety levels – giving rise to resurfacing concerns about passenger safety.