Investigators not sure how large spill is
                                
                                
                                    (Newser) -
                                    Oil spilled into the Mississippi River yesterday when a barge carrying 80,000 gallons of it hit a railroad bridge in Vicksburg, Miss., the AP reports. Investigators don't know how much oil spilled, but a sheen was reported as far as three miles downriver. A second barge owned by...