These must have been the students final projects.
From The Jakarta Globe July 19
Dozens of Bombs Found in Indonesian Boarding School
Police found more than two dozen home-made bombs in eastern Indonesia following an explosion last week inside an Islamic boarding school suspected of being a bomb factory, a spokesman said on Tuesday.
After the blast that killed a suspected terrorist, police raided the Umar bin Khatab school in West Nusa Tenggara province and ended a three-day standoff on Wednesday with students and teachers armed with swords, machetes and sticks.
Police later found the home-made bombs, but did not say exactly when.
“The 26 pipe bombs were defused,” national police spokesman Anton Bachrul Alam told reporters. “They planned to use the bombs to attack police stations.”
Police said that the school was linked to radical cleric Abu Bakar Bashir, who was jailed for 15 years last month for funding a terrorist group that was planning attacks against Westerners and political leaders.
Most of Indonesia’s 200 million Muslims are moderates, but the country has struggled to deal with a radical fringe of extremists who have carried out numerous attacks including the 2002 Bali bombings that killed 202 people.