Two residents of the east-central Iowa city of Grinnell are in federal custody for their alleged role in a drug trafficking operation. Gary Lee Christianson and Marylin Zarger were both arrested last week after an investigation involving the Jasper-Poweshiek-Pella Drug Task Force, The Poweshiek County Sheriff’s Office, The Grinnell Police Department, and the U.S. Postal Inspector’s Office. The investigation started in November after several suspicious mail package deliveries. Over the past few weeks, a large sum of cash, a large amount of crystal meth, and some black tar heroin have been located and seized. All the items were sent through the mail. Christinson is suspected of being involved in the delivery of meth and heroin. He is being held on a federal parole violation. Zarger is also believed to be involved in the trafficking of the drugs. No further details are available. Earlier this year, two other Grinnellians were arrested after receiving marijuana through the mail.