Piles of concrete caved in on hundreds of mostly teenage boys last week in the collapse of the Al Khoziny Islamic boarding school in the Indonesian town of Sidoarjo, in East Java province, trapping and later killing them.
Using excavators, rescuers late on Sunday cleared 80 per cent of the debris and found bodies and body parts of the mostly teenage victims, the disaster mitigation agency said in a statement.
Budi Irawan, a deputy at the disaster mitigation agency, said a total of 50 people had died based on the bodies recovered and rescuers were expected to finish their search by the end of Monday for 13 more trapped victims.
"The number of victims is the biggest this year from one building," he told a media conference.
"Out of all the disasters in 2025, natural or not, there hasn't been as many dead victims as the ones in Sidoarjo."
Yudhi Bramantyo, a search and rescue agency official, said at the same news conference that five other body parts were found, indicating the death toll was likely at least 54 people.
Rescuers are continuing their search, with footage shared by the search and rescue agency showing recovery workers carrying orange body bags out of the ruins of the school.
Authorities have said the cause of the collapse last Monday was construction work on the upper floors that the school's foundations could not support.
Across Indonesia, there are about 42,000 Islamic school buildings, known as a pesantren, data from the country's religious affairs ministry shows.
Only 50 pesantren have building permits, Dody Hanggodo, the country's public works minister, was quoted by local media as saying on Sunday.
It is not immediately clear if Al Khoziny had a building permit.
Reuters could not immediately contact school authorities for comment.
