Snohomish County authorities seized more than $550,000 in cash and 23 pounds of heroin when they served search warrants last week in the Lake Serene neighborhood and in Shoreline.
The operation by the Snohomish Regional Drug & Gang Task Force resulted in the arrest of five men and three women.
Authorities said the drugs seized are believed to be associated with the Mexican Sinaloa drug cartel.
Those arrested include a 22-year-old California man, a 30-year-old Everett man, a 26-year-old woman and 27-year-old man from Shoreline, and two men, ages 28 and 29, from Lynnwood.
The Task Force served several search warrants on three locations, which led to additional search warrants on various vehicles.
In addition to the drugs and money, agents also seized six vehicles, a house and property.
Police said the street value of the drugs was estimated to be $1 million.