Indonesian rescuers have recovered the bodies of at least 54 students after a prayer hall at an Islamic boarding school collapsed last week, officials said Monday, as search efforts continue for 13 others still missing.

Using heavy excavators, jackhammers, circular saws—and at times, their bare hands—rescue workers cleared tons of rubble over the weekend at the century-old Al Khoziny Islamic Boarding School in Sidoarjo, East Java.

Over the weekend alone, 35 more bodies were found. In total, we have retrieved 54 victims, including five body parts,” said search and rescue official Yudhi Bramantyo at a press briefing.

We hope to conclude the recovery operation today, he added.

The hall collapsed on September 29 while hundreds of students—mostly boys aged 12 to 19—were attending prayers. Ninety-seven survivors were treated for minor injuries and released, while six others remain in hospital with serious injuries.

Police say the building had been under illegal construction, with two additional floors being added to the existing two-story structure without a permit. Authorities believe the structure gave way while workers were pouring concrete for the third floor.

The construction couldn’t support the load because it didn’t meet the proper standards,” said Mudji Irmawan, a construction expert from the Tenth November Institute of Technology. “Students should never have been inside during construction.

Sidoarjo district chief Subandi confirmed that the school had not obtained a required building permit.

Many extensions in traditional boarding schools are built without permits, especially in rural areas, he said.

Under Indonesia’s 2002 building code, construction without a permit is punishable by fines and imprisonment, with up to 15 years in prison and an 8 billion rupiah (about USD 500,000) fine if violations cause deaths.

The school’s caretaker, respected cleric Abdus Salam Mujib, made a rare public appearance after the tragedy, apologising and calling for patience.

This is God’s will, and we must remain patient,” he said. “May God reward those affected with something better.

East Java’s police chief, Nanang Avianto, said a full criminal investigation is underway.

We will investigate this case thoroughly, he told reporters.