SIDOARJO, Indonesia (AP) — Indonesian crews recovered a dozen bodies Monday as they searched for young people missing after a prayer hall at an Islamic boarding school collapsed last week, bringing the death toll to 61.

The structure caved in on Sept. 29 when the students, mostly boys between the ages of 12 and 19, were performing afternoon prayers. The building at the century-old Al Khoziny school in Sidoarjo on Indonesia’s Java island was undergoing an unauthorized expansion.

Only one student escaped unscathed, authorities said, while 99 were treated for injuries and released. Four suffered serious injuries and remained hospitalized Monday after undergoing amputations.

With no more signs of life from beneath the tons of rubble three days after the collapse, authorities last week turned to heavy excavators to help them progress more rapidly.

The National Disaster Management Agency said rescue workers pulled 12 bodies and at least seven body parts from the rubble Monday. They continued their search for two students reportedly still missing. No survivors are expected.

Authorities said most of the bodies were in a condition that made them difficult to identify. Grief-stricken relatives provided DNA samples to help with identification at the Bhayangkara police hospital in the neighboring city of Surabaya, the capital of East Java province.

The Disaster Victims Identification teams said they had managed to identify 17 bodies by Monday and had handed over them to their families for funerals.