The owner of a New Hampshire gunpowder plant where two workers were killed in a 2010 explosion has been convicted of negligent homicide and manslaughter. New Hampshire Public Radio reported that Craig Sanborn, 64, of Maidstone, Vt., was found guilty Wednesday afternoon in Coos County Superior Court. He was the owner of the Black Mag plant in Colebrook, where an explosion killed Donald Kendall of Colebrook and Jesse Kennett of Stratford. Prosecutors said Sanborn was motivated by profit and failed to ensure employee safety. Sanborn’s lawyer said Sanborn was away and had no control over the plant.