Officers from the Northeast Iowa Drug Task Force served a search warrant at a home at 302 Sumner Street in Decorah Thursday night.
Police say they discovered methamphetamine, marijuana, hallucinogenic substances, drug paraphernalia, prescription medicines and cash.
Four people were arrested on multiple drug charges: 25-year-old Aaron Lowe, 24-year-old Cody Cronin, 45-year-old Marleen Dahl-Hayek and 26-year-old Samantha Jones.
Police say their investigation is still going on and additional charges will be filed against all four.
The Decorah Police Department, Winneshiek County Sheriff's Department, Iowa State Patrol and Chickasaw County Sheriff's Department participated in the search, with help from the Winneshiek County Attorney's Office.