BALTIMORE (AP) — Investigators on Tuesday were trying to determine what caused an explosion aboard a cargo ship laden with coal as it departed Baltimore's harbor for East Africa. Officials said no one was injured in the blast Monday evening, which prompted a mayday call when it was reported near the site of last year’s Francis Scott Key Bridge collapse. Video of the explosion showed flames shooting high into the air, followed by a large plume of dark smoke billowing over the Patapsco River.