U.S. citizen John Edward Tobbin, arrested in the Russian city of Voronezh, south of Moscow, may be sentenced to a prison term of up to 10 years. Given the crimes Tobbin is charged with the court may sentence him to a prison term ranging from five to 10 years, senior investigator Andrei Makarov said on Wednesday. He said the investigation is in its final stage. "Several investigative actions remain to be conducted after which the case will be sent to court," Makarov said, adding that the investigation may end before the date set earlier - March 26. Before the end of the pre-trial investigation the number of charges brought against Tobbin may increase, Makarov said. The current charges against Tobbin include illegal ownership or storage for sale or repeated sale of large amounts of illegal drugs and running a 'drug den'. These charges entail prison sentences of up to ten and up to four years, respectively, Makarov said. Tobbin had nearly 2.5 grams of marijuana on him when he was arrested in Voronezh on February 1. Makarov said he did not intend to release Tobbin on bail or against a written pledge not to leave the city. He said the American has had no complaints about the conditions of his confinement, Interfax reports. Tobbin is a post-graduate student of Voronezh university working on a thesis on changes in the political priorities of Russians over the past 10 years. He came on a Fulbright Foundation scholarship with recommendations from the U.S. State Department. Makarov said Tobbin had studied Russian at a U.S. military- sponsored school in Monterey, Calif., and received military intelligence training at Fort Huachuca, Arizona where he earned a diploma as an expert on interrogations.