SIDOARJO, Indonesia — On Wednesday, rescuers kept up their efforts to locate dozens of missing students believed to be trapped under the ruins of a school that collapsed in East Java province.

The disaster on Monday has claimed six lives, as reported by Yudhi Bramantyo, the Deputy Chief of Operations at the National Search and Rescue Agency.

Five survivors were successfully rescued after a tunnel was dug at the base of the building to their location.

“Their situation seemed to improve as we detected them yesterday. They have been able to communicate even though they are trapped under concrete,” Bramantyo stated. “We started providing them with food and water yesterday.”

Rescuers are racing against the clock in the search for other survivors, with dozens of students still unaccounted for, he added.

The incident occurred around 2:30 p.m. on Monday when the structure gave way over a large number of people in a prayer hall at the historic al Khoziny Islamic boarding school, located on Java island’s eastern side.

Most of the students were boys aged between 12 and 18, studying from grades seven to 12. According to survivors, the girls were praying in a separate area of the building and managed to escape the disaster.

Most rescues typically happen within 24 hours after such disasters, with chances of survival decreasing each day after. More than 300 workers continued to work to try and reach those who have been detected to be still alive and trapped below.

“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 lives of those we have detected within the golden hours.”

In a sign of hope, rescuers pulled one boy out alive on Wednesday afternoon, loading him gently onto a stretcher to be taken to a hospital. His condition was not immediately known.

Of the approximately 100 injured, more than two dozen are still hospitalized, with many said to have suffered head injuries and broken bones, authorities said.

Before Wednesday’s rescue, Syafii’s agency said at least six children were alive under the rubble, but the search has been complicated with the slabs of concrete and other parts of the building remaining unstable. Heavy equipment is available but is not currently being used due to concerns that could cause further collapse.

Rescuers in hardhats crawled through tight passages made of concrete blocks, steel bars and rubble collapsed in the debris, chipping away at it with hammers and hand-held power tools to try and reach those still underneath.

Oxygen, water and food has been sent through narrow gaps to those still trapped under the debris to keep them alive. Search teams have also used detectors and thermal drones to detect potential survivors who could be rescued.

The Islamic boarding school was undergoing an unauthorized expansion to add two new levels when it collapsed during afternoon prayers, authorities said. The prayer hall was two stories high but two more were being added without a permit, according to authorities. Police said the old building’s foundation was apparently unable to support two floors of concrete and collapsed during the pouring process.

Authorities initially said 38 people were missing, but revised that upward on Tuesday after consulting attendance lists and talking with families.

“In the early stages there will inevitably be some confusion about the data,” said Suharyanto, the head of the National Disaster Mitigation Agency, who only goes by one name as is common in Indonesia.

Tarigan reported from Jakarta, Indonesia.