Jakarta. Police investigators have discovered a total of seven homemade explosive devices at SMA Negeri (state high school) 72 Jakarta, including two that detonated during last Friday’s explosion that injured dozens of students and teachers, a senior officer said on Tuesday.

The suspected perpetrator -- a student at the same school -- remains under treatment at the Bhayangkara Police Hospital with severe head injuries. Authorities have withheld the student’s identity because he is a minor.

A bomb squad from the Jakarta Metropolitan Police Mobile Brigade (Brimob) found five undetonated explosive devices and two small craters created by the earlier blasts inside the school’s mosque in Kelapa Gading, North Jakarta, said Chief Commissioner Henik Maryanto, commander of the Brimob unit.

“We found a total of seven bombs at the site, two of which had already exploded. The bomb squad then neutralized several active devices and secured additional explosive materials,” Henik told reporters at a press conference in Jakarta.

He added that preliminary analysis suggested the twin blasts originated from two separate bombs placed inside the mosque. The explosions damaged the mosque’s floor and walls and caused panic among students and staff. Police are still examining the type of explosive materials and how the devices were assembled.

Further searches uncovered four more homemade bombs in the school’s waste disposal area about 50 meters from the mosque -- two were still active when found, while the others had already detonated, Henik said.

Another device was discovered in the school library, made from a soft drink can and equipped with a fuse and a remote-control trigger.

“Based on our initial assessment, it is very likely that the bombs were detonated remotely rather than from inside the mosque,” Henik said.

All evidence has been transferred to the National Police Forensic Laboratory for detailed analysis, including the explosive compounds used, triggering mechanisms, and whether the devices were designed to detonate in sequence.

The explosion occurred during Friday prayers, when students and teachers were gathered inside the mosque. More than 90 people were injured, most suffering hearing loss and minor burns from the blast’s shockwave.

Police have not yet disclosed a possible motive, but investigators believe the incident was premeditated and are continuing to assess the student’s background and potential influences.