I still didn’t understand where the other elementals and hybrids had come from. Later, I found out that Kira and Jakob had shut off the gas to the individual cells for the Hybrids. Because of the dangerous powers of the elementals and the fact that they could travel through various materials, the only way to keep them from escaping was to sedate them.

This way, they were easy to transport from the cells to the lab and back into their cells. 

By shutting off the main gas supply to the cells, the hybrids started waking up. Jakob ran through the cells to release all of them as Kira moved the ones who could not move. Naturally, the Shadow Elemental Hybrids showed up but they were easily taken care of since the prisoners greatly outnumbered the caretakers.

Jakob then led them, for revenge, to the most likely place that Rheidan would be. His lab.