EDMONTON - RCMP seized and burned over 5,000 marijuana plants from a dozen rural greenhouses Wednesday in one of the largest outdoor seizures in Alberta's history.

"Picture three million joints," RCMP spokesman Wayne Oakes said. "That's almost enough for everyone in the province of Alberta."

Following up on a tip, RCMP found the grow operation near Evansburg, 90 kilometres west of Edmonton.

The 12 greenhouses, on two separate sites, were in a remote area accessible only by a single road and hidden by thick brush from the main highway. Police refused to give the exact location.

RCMP, acting with Edmonton police, raided the two sites early Wednesday morning. They seized 5,523 plants and arrested four men. Charges and further arrests are expected, Oakes said.

The marijuana ranged in maturity from small cuttings to plants ready for harvest. Eleven kilograms of processed marijuana were also seized.

They were grown in 12 simple plastic-covered frames on two separate properties. No hydroponic equipment or weapons were reported.

Both locations were very close to Chip Lake, giving easy access to abundant water, Oakes said.

"That likely contributed to the success. It was a fairly sophisticated operation," Oakes said.

He wouldn't put a dollar figure on the find, saying it "might lure other people to participate in this type of activity." But in a similar operation last summer, RCMP seized 2,300 plants from nine outdoor sites and estimated the street value at more than $2 million.

In a separate investigation on Wednesday, Vegreville RCMP seized 414 mature marijuana plants along with harvested marijuana and a long-barrelled rifle near Mundare. That find is estimated at $200,000.

Two suspects fled when police arrived but were tracked down by a police dog and his handler.

Mundare resident Joseph Ralph Scianimonico, 58, and Onoway residents Daniel Anthony Dea, 29, and Patricia Grace Dea, 29, were all charged with production and possession of controlled substances in connection with the Mundare investigation.