The Al Khoziny school in the town of Sidoarjo in East Java province caved in on Monday, cratering upon hundreds of teenage students during afternoon prayer, its foundations unable to support ongoing construction work on its upper floors.
Thirty ambulances were prepared as rescuers continued looking for 50 students - mostly teenage boys from the ages of 13 to 19 - still trapped under the rubble, the disaster mitigation agency said.
Earlier on Friday, the agency reported nine had died, adding that rescuers had received the parents' permission to make use of heavy equipment after failing to find signs of life during previous efforts.
"Every family of the victims has given their blessing if the heavy equipment gets in there and disturbs the bodies beneath the rubble," agency chief Suharyanto said, adding that there was a possibility that more dead bodies would be found.
Alongside the ambulances were cranes deployed to excavate some of the debris.
Rescuers dug through tunnels in the remains of the building, calling out the boys' names and using sensors to detect any movement but found no signs of life, photos shared by the search and rescue agency showed.
Fourteen rescued victims were receiving medical treatment, the disaster agency said.
Al Khoziny is an Islamic boarding school known locally as a pesantren.
Indonesia, the world's largest Muslim-majority nation, has a total of about 42,000 pesantren serving seven million students, according to religious affairs ministry data.
