BRASILIA  - A Brazilian doctor who was charged with killing seven patients to free up beds at a hospital intensive care unit may have been responsible for as many as 300 deaths, according to a Health Ministry investigator. Prosecutors said Dr Virginia Soares de Souza and her medical team administered muscle relaxing drugs to patients, then reduced their oxygen supply, causing them to die of asphyxia at the Evangelical Hospital in the southern city of Curitiba. De Souza, a 56-year-old widow, was arrested last month and charged with seven counts of aggravated first degree murder.