The death toll from the collapse of a school in Indonesia has risen to 54, authorities said, with rescuers still searching for more than a dozen missing people.

Hundreds of students, most of them teenage boys, had gathered for prayers at the Al Khoziny Islamic boarding school in East Java when it collapsed last Monday while undergoing construction.

Indonesia’s disaster mitigation agency says it is the country’s deadliest disaster this year. Rescuers are expected to complete their search for 13 victims trapped under the rubble by the end of the day.

Investigators are still looking into the cause of the collapse. Some officials said the two-storey building caved in because its foundation was unstable.

“Out of all the disasters in 2025, natural or not, there hasn’t been as many dead victims as the ones in Sidoarjo,” Budi Irawan, a deputy at the disaster mitigation agency, told a press conference.

The toll includes at least two people who were freed from the debris but later died in hospital.

Al Khoziny is a traditional Islamic boarding school in Indonesia known as a pesantren.

Many pesantren operate informally, without strong regulation or consistent monitoring. It is unclear if Al Khoziny had a permit to undertake additional construction.

Search and rescue operations have been challenging because of the way the building had collapsed, leaving only narrow voids for rescuers to maneuver in, authorities said last week.

Survivors have spoken of their harrowing escapes to local media.

Muhammad Rijalul Qoib told Detik News he first “heard the sound of falling rocks”, which “got louder and louder”.

The 13-year-old ran for the door immediately, and while he managed to escape, he was wounded by falling debris from the roof.