MASON CITY — A Mason City man has pleaded not guilty to federal drug charges. 34-year-old Demetrius Johnson was recently indicted on charges of conspiracy to distribute methamphetamine, three counts of possession with the intent to distribute meth, as well as possession of a firearm by a prohibited person. The US Attorney’s Office for the Northern District of Iowa says Johnson was part of a meth-dealing operation in north-central Iowa between the fall of 2017 and this month. Johnson was previously convicted on a state-level charge of delivery of cocaine in Cerro Gordo County. He started serving a 15 year prison sentence on that charge in 2016. Johnson pleaded not guilty in US Federal Court on Friday. His trial is now scheduled to start on November 4th.