Indonesian officials and rescue workers continued their search for survivors on Wednesday, as some 91 students were still believed to be trapped under the rubble of a collapsed school building in Java.

The multi-story Islamic boarding school collapsed on Monday during an ongoing illegal construction of a third and fourth floor. The structure fell as students were gathered in the hall for afternoon prayers. 

Most of those unaccounted for are boys between the age of 12 and 18. Female students were gathered in a different hall for prayers and managed to escape.

Rescue workers 'racing against time'

More than 300 rescue workers, police officials and soldiers continue to work through the debris. Most rescues typically happen within 24 hours of a disaster with chances of survival decreasing after that.

"Based on student attendance data, 91 people are suspected to be buried under building materials," national Disaster and Mitigation Agency spokesperson Abdul Muhari said late on Tuesday.

However, on Wednesday, officials said they were still trying to confirm the number of people missing when asked at a news conference.

"We hope that we can complete this operation soon," Mohammad Syafii, head of Indonesia's National Search and Rescue Agency, told reporters at the news conference. "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," he said. 

At least six children are alive under the rubble, the agency said, adding that the rescue operation has been complicated due to unstable blocks of concrete in the collapse.

Three people have been confirmed dead so far and 100 others injured. Of those injured, 26 have been hospitalized. The death toll is likely to rise once officials move from rescuing survivors to retrieving the deceased from the rubble.

Edited by: Wesley Dockery