(KRON) -- The Alameda County Sheriff's Office (ACSO) announced Tuesday its conclusion of a long investigation into a drug trafficking organization in the Bay Area that operated the sale of fentanyl. According to the sheriff's office, the investigation culminated after a multi-location search warrant that ended in East Oakland. A total of $155,000 in cash and 28 kilograms (or about 61 pounds) was recovered from the operation. Authorities say that amount of fentanyl is valued to be more than $700,000. Alameda County supervisors inching closer to pick for DA Twenty-eight kilograms of fentanyl and $155,000 in cash were recovered after a multi-location search warrant operation. (Photo: Alameda County Sheriff's Office) Three men and one woman were arrested and booked into Santa Rita Jail for charges including conspiracy and drug possession for sale, according to the sheriff's office. Alameda County Narcotics Task Force conducted the investigation with assistance from ACSO and the California Department of Justice.