Sidoarjo: Indonesian rescue workers were racing against the clock on Wednesday in the search for survivors from a school collapse in East Java province, with at least 91 students still unaccounted for, along with three confirmed dead and about 100 injured.

The Islamic boarding school, undergoing an unauthorised expansion to add two new stories, collapsed during afternoon prayers on Monday, sending slabs of concrete and heavy debris onto the students below.

Most rescues typically happen within 24 hours, with survival chances decreasing thereafter. More than 300 workers continued to work desperately at the scene to reach those detected as still alive and trapped.

“We hope that we can complete this operation soon,” Mohammad Syafii, head of Indonesia's National Search and Rescue Agency, told reporters. “We are currently racing against time because it is possible that we can still save the lives of those we have detected within the golden hours.”

Of the approximately 100 injured, 26 remain hospitalised, many with head injuries and broken bones, authorities said. Syafii's agency said at least six children are alive under the rubble, though unstable slabs prevent heavy equipment from being used safely.

Rescuers in hard hats crawled through tight passages of concrete blocks, steel bars and rubble, chipping away at debris with hammers and hand-held power tools. Oxygen, water and food have been sent through narrow gaps to those trapped. Thermal drones and detectors are also in use to locate potential survivors.

The collapse occurred around 2:30 pm on Monday at the century-old Al Khoziny Islamic boarding school in Sidoarjo. The students were mostly boys in grades seven to 12, aged 12 to 18. Female students praying elsewhere in the building escaped.

The prayer hall was two stories high; two additional floors were added without a permit. Authorities said the old foundation could not support the extra concrete, causing it to collapse during pouring.

Initial reports listed 38 missing, later revised to 91 after attendance checks and family consultations.

“In the early stages, there will inevitably be some confusion about the data,” said Suharyanto, head of the National Disaster Mitigation Agency.