SIDOARJO - Rescuers searching for people trapped under a collapsed school in Indonesia are hoping to dig a tunnel, at the risk of destabilising the rubble, to reach an estimated 59 still missing.
Part of the multi-storey boarding school on the main island of Java suddenly gave way on Monday as students gathered for afternoon prayers.
School records showed 91 people were buried under the rubble, according to the National Disaster and Mitigation Agency, and at least five people have been confirmed dead.
Around 59 people remained trapped as of Wednesday night, agency spokesman Abdul Muhari said in a statement on Thursday, cautioning that the data was "dynamic and changing" as some people who survived the incident have not yet come forward.
Distraught and tearful families waited anxiously near the site for news of their loved ones. Local residents near the school offered the families to stay in their homes as they waited, AFP saw.
Rescuers pulled five survivors from the rubble on Wednesday as frantic parents demanded searchers speed up efforts to find dozens of children believed to still be trapped.
Investigations into the cause of the collapse in the town of Sidoarjo are ongoing, but initial signs point to substandard construction, experts have said.
The rescue operation is complex as vibrations happening in one place can impact other areas, said Mohammad Syafii, head of the National Search and Rescue Agency.
"So now, to reach the spot where the victims are, we have to dig an underground tunnel," he told reporters.
But digging itself poses challenges, including possible landslides. And any tunnel will only provide an access route around 60 centimetres wide because of the structure's concrete columns.
Thermal-sensing drones are being used to locate survivors and the deceased as the 72-hour "golden period" for best survival chances comes to an end.
But the operation could last longer than seven days if people are still missing, a search and rescue agency official told AFP.
Signs of life have been detected in several areas, said rescue official Emi Freezer of the National Search and Rescue Agency.
Water and food was being sent in, but access was through a single point, he said.
"The main structure has totally collapsed," he added.
The operation was complicated by an earthquake, which struck offshore overnight Tuesday to Wednesday, briefly halting the search.
Local charitable organisations have set up posts offering families food and drink around the ruins.