Alberta Law Enforcement Response Team spokesman Mike Tucker says the four were arrested following searches of three homes and two storage lockers in Edmonton last month.
One of the homes had a full-blown, industrial steroids manufacturing laboratory and was just metres away from an elementary school.
Tucker says more than 360,000 pills, 10,000 vials and over three dozen types of liquids and powders were seized. The value of the materials is pegged at $9.3 million.
Police allege the illegal steroids were distributed as far away as St. John's, N.L., and possibly internationally
"These individuals are allegedly responsible for a large, illegal, underground steroid distribution network that spans across Canada and these investigators have literally cut the head off the snake," said Insp. Darcy Strang said Thursday.
"We believe this has literally shut down the sale of steroids in Alberta, significantly."
Kirk Goodkey, 40, of Edmonton is charged with possession for the purpose of trafficking and possessing the proceeds of crime.
Parmjit Brar, 40; Jordan Quiring, 27; and Alexandria Edwards, 27, each face similar charges.
Tucker said more charges are being contemplated.
The lab that officers discovered contained a pill press, powder mixer, two fume hoods, a spectrometer, glassware and beakers and a large amount of packaging materials.
Inside one of the storage lockers investigators found nearly 100 barrels of unknown chemicals.
The Edmonton fire department's hazardous materials team helped with testing and decontamination.
The drugs were being sold under the name USP, an acronym that stands for underground steroid pharmaceuticals.
"I think it spans all across society for the most part. Anybody who wants to be bigger, better professional athletes, bodybuilders — even kids who may want to be a bit larger — often end up falling into this trap, unfortunately," Strang said.
Four high-end vehicles and $88,000 in cash were also seized.
Tucker said the investigation began in May 2014 and remains ongoing.
ALERT says the largest steroids bust in Canada previously was in December 2008 when police in Quebec seized more than 400,000 tablets from a home in Thérèse-De Blainville, Que.