The number of students confirmed dead after the collapse of an Islamic boarding school building in Indonesia rose to 36, from 16 a day earlier, the country's disaster mitigation agency said on Sunday.

Efforts continued for a seventh day to search for the bodies of 27 students still declared missing - mostly teenage boys from the ages of 13 to 19 - trapped under the rubble, the agency said.

Cranes were deployed to excavate debris and search and evacuation efforts were 60% complete, according to the agency, which said it expected to clear all debris and finish the search on Monday.

The Al Khoziny school in the town of Sidoarjo in East Java province caved in last Monday, collapsing on top of hundreds of teenage students during afternoon prayers, its foundations unable to support ongoing construction work on its upper floors.

On Friday, rescuers received the parents' permission to make use of heavy equipment after failing to find signs of life during previous efforts.

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.

Al Khoziny is an Islamic boarding school known locally as a pesantren.

Indonesia, the world's largest Muslim-majority nation, has about 42,000 pesantren serving 7 million students, according to religious affairs ministry data.