SURABAYA, Indonesia (AP) — Indonesian rescuers searched for possible missing passengers Monday after rescuing 231 people from a ferry that caught fire the previous day off the main island of Java, leaving at least five people dead. Passengers described leaping overboard and staying afloat for hours before rescue.

The Mutiara Sentosa 2 ferry was traveling from Indonesia’s second-largest city of Surabaya in East Java to the city of Makassar in South Sulawesi. Initial reports said it was carrying 271 people, including 39 crew members, based on the ship’s manifest, when the fire broke out between 6 a.m. and 7 a.m.

However, by Monday officials said many more people were aboard than listed, and the number of people missing was unclear. Officials were relying on reports from families of victims and survivors in an attempt to determine the number of the missing.

It is common in Indonesia for the number of passengers on a boat or ferry to differ from the manifest. Such discrepancies can complicate search and rescue efforts, said Nanang Sigit, the search mission coordinator who also heads the Surabaya Search and Rescue Office.

The cause of the fire remained under investigation. Indonesian navy ships assisted, along with a number of passing vessels, at the scene about 35 kilometers (22 miles) north of Sapudi island in the Sumenep regency.

The vessel was also loaded with 180 vehicles, mostly trucks.

Ahmad Abdul Karim, a survivor, said the fire appeared to have started in a truck on the lower vehicle deck.

“Fanned by the wind, the flames spread extremely quickly,” Karim said, “In less than 30 minutes, everyone had been instructed to move to the bow of the ferry.”

Another passenger, Azhari, said many passengers had just woken up when the fire erupted, apparently from the rear of the ferry.

“The fire spread quickly to the middle of the vessel,” Azhari, who goes by a single name, said in a television interview. “There was no other option for us but to jump into the sea.”

He said passengers were in the sea for about four hours before passing vessels began pulling them to safety.

Television news showed exhausted survivors disembarking from a rescue vessel at a harbor in Surabaya, while rescuers transported bodies to ambulances and grieving relatives waited for information.

Transportation Minister Dudy Purwagandhi said the government would review the performance of the ferry’s operator, Atosim Lampung Pelayaran, after the National Transportation Safety Committee, or KNKT, completes its investigation.

“First we need to determine the cause based on KNKT’s findings,” Purwagandhi said.

The ferry was built in Japan in 1992 and was sold to Indonesia in 2015. With a length of 160 meters (525 feet), it can accommodate 689 passengers and 49 crew, along with up to 181 vehicles.

The Mutiara Sentosa 2 serves the Surabaya-Makassar route, a voyage that typically takes around 40 hours and is primarily used by domestic travelers and cargo transport between the islands of Java and Sulawesi.

Indonesia is an archipelago of more than 17,000 islands where ferries are a common method of travel. Disasters occur regularly, with weak safety enforcement often blamed.

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Associated Press journalists Niniek Karmini and Edna Tarigan in Jakarta, Indonesia, contributed to this report.