The Philippines has sent coast guard, military and civilian ships to search for survivors on a smouldering passenger-cargo vessel off the western province of Palawan, where a fire killed at least five people and more than 80 people are unaccounted for.

The Coast Guard released drone footage of the blackened ferry surrounded by clear blue-green waters, which the ferry continues to smoke hours after it had been engulfed by fire Wednesday night.

Heavy smoke still billowed from the ship and extreme heat, and the danger of explosions hampered rescuers from getting aboard, said Commodore Noemie Cayabyab, a spokesman for the Coast Guard.

Two Chilean nationals have been rescued from the boat, which was en route from Baseco, in Manila, to Coron, a resort town in Palawan that is a favourite among tourists because of its diving spots and island-hopping opportunities, so far.

The Coast Guard had already sent two 44-metre boats and three smaller boats, and since Wednesday night, army rescue boats, local fishermen and private resort owners have participated in the search, Cayabyab said. Also on standby was one military aircraft, she said.

The explosion, which was “heard from the cargo hold,” was reported by at least one survivor as the blaze quickly engulfed the entire ferry, Cayabyab said at a press conference. The survivor said it was a huge blast, but authorities have not yet figured out what caused it, she said.

Some of the survivors rescued from the sea did not have life jackets on, which meant that passengers may have jumped overboard as the fire spread, Cayabyab said.

The vessel has been subjected to safety inspections.

The vessel’s manifest listed 117 passengers and 17 crew members aboard and a capacity of 330. The boat had undergone safety checks, Cayabyab said.

It was also carrying five motorcycles, an electric vehicle, ​a forklift, a pickup truck ​, and mostly cargo goods, she ⁠said.

A full investigation will be made by the Coast Guard, and Cayabyab said he was aware of that. She said it was not yet possible to come to any conclusions and the investigation was continuing over whether authorities were looking into a possibility of sabotage or a terrorist attack.

The owner of the ship, Atienza Inter-Island Ferries, assured that the boat is 100 per cent supporting government efforts in the investigation of the incident.

The company said in a statement that it was working around the clock and all available resources were being mobilised to “dominate this crisis”, while it would be “committed to transparency” as the investigation continued.

Ferry transportation is widely used in the Philippines, a country of over 7,600 islands, and where millions depend on boats to get from province to province.

The country has a spotty history of maritime safety, and many past ferry failures have been attributed to overcrowding, rough seas, and lax safety inspections.