Bazlus Samad and Mahmudur Rahaman Tapash were charged with "death due to negligence." The case against them seems pretty strong, too: the top three stories of the eight-story building were added illegally (a ninth story was under construction at the time of the collapse), and survivors have said that though they were ordered by police to evacuate the building the night before the collapse after cracks appeared in the walls, their bosses ordered them back in to work.
Following a tremendous outcry and pressure to respond, Bangladesh Prime Minister Sheikh Hasina ordered the arrests of the owners of the factories housed within the building as well as the owner of the building itself, Mohammed Sohel Rana. Rana has yet to be found, and Bangladesh News 24 hours reported that "several people who identified themselves as Rana's staff were seen moving goods from the house."
The night before the building collapse, Rana reportedly told workers that the building "would stand 'for another 100 years.'" It didn't even last another 100 hours.