Wichita ? A Wichita student, 13, took a homemade bomb in his backpack for the past two weeks around his middle school before anyone noticed, authorities said Thursday.

The explosive device was found Wednesday afternoon at Brooks Technology and Arts Magnet Middle School in Wichita. Another student saw the device and showed it to his father, who took it to school administrators.

Police were notified, and the bomb squad disposed of the device. The student who brought the device to school didn’t threaten anyone, police Capt. Terry Nelson said.

Gordon Bassham, a police spokesman, said no formal charges had been filed yet against the student, and the boy’s motive for making the device is unknown.

Police said the device, which measured about 5 inches long and was less than an inch in diameter, was made out of metal casings filled with pieces of a fireworks sparkler that had been ground down into powder.

The bomb had a fuse taped to one end.

Nelson said the device, though fairly small, would have caused injuries had it been ignited.

“Anyone standing in close proximity would have been injured,” he said.