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, BBC reported.

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, according to BBC.