Foxconn has reopened its Chengdu, China plant following an explosion last month that killed three employees and injured numerous others. AllThingsD reports that the company has also concluded its investigation into the incident, but has yet to release the results. The upper floors of the building are home to iPad 2 production lines, which had been shut down since the May 20 incident; Ticonderoga Securities analyst Brian White said in a note to clients—quoted…