Part of the multi-story boarding school suddenly collapsed on Monday as students gathered for afternoon prayers.

After days of rescue operations, 59 people were still feared buried under the rubble after at least five people had been confirmed dead.

"We used high-tech equipment like thermal drones, and, scientifically, there were no more signs of life," said Suharyanto, head of the National Disaster Mitigation Agency (BNPB).

Distraught and tearful families waited anxiously near the site for news of their loved ones. Residents near the school offered the families to stay in their homes as they waited, AFP saw.

"I've been here since day one. I am hoping for the best news, that my brother survives. I am still hopeful," said Maulana Bayu Rizky Pratama, whose 17-year-old brother is missing.

"It's been four days, I hope my brother will be found soon. I feel sad thinking of him being down there for four days," the 28-year-old added.

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.

Abdul Hanan, whose 14-year-old son is missing, said children under the rubble had been crying for help.

"The rescue operation must be accelerated," he urged.

Investigations into the cause of the collapse are ongoing, but initial signs point to substandard construction, experts have said.

Complex operation

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 (Basarnas).

"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 destabilizing the rubble. And any tunnel will only provide an access route around 60 centimeters 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.

The families of the missing agreed on Thursday for heavy equipment to be used, Coordinating Human Development and Culture Minister Pratikno said, adding that rescuers would exercise "extreme caution".

But the operation could last longer than seven days if people are still missing, a Basarnas official told AFP.

The school collapse was so violent it sent tremors across the neighborhood, said local resident Ani.

"I felt a vibration and then I heard a noise. I immediately ran to save myself. I didn't realize at first it was a building collapse," the grocery stall owner told AFP.

AFP saw rescuers in orange uniforms appearing to snake cameras under the rubble to hunt for traces of survivors.

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 organizations have set up posts offering families food and drink around the ruins.

The building folded after its foundation pillars failed to support the weight of new construction on the fourth floor of the school, said the BNPB.

Lax construction standards have raised widespread concerns about building safety in Indonesia, where it is common to leave structures, particularly houses, partially completed, allowing owners to add extra floors later when their budgets permits.

This month, at least three people were killed and dozens injured when a building hosting a prayer recital collapsed in West Java.