Police say an ongoing operation near Kersbrook in the Adelaide Hills has so far yielded a quantity of illegal drugs with an estimated street value of $85 million.

In March, a police patrol on the look out for arsonists uncovered several kilograms of amphetamines buried along the side of Mount Gawler Road at Inglewood.

Two men were later arrested.

Police have conducted three searches of the same area since, unearthing 10 and a half kilograms of amphetamines, 21,000 ecstasy tablets and one kilogram of cocaine.

Detective Chief Inspector Steve Taylor says the latest find was uncovered two days ago and the size of the haul indicates organised criminal groups are responsible.

"We're continuing to work very hard on identifying the key members of the network and it's our end goal and our objective to gather further evidence and completely dismantle that network," he said.

"It's certainly a very significant seizure and we're very pleased that we're able to have a very significant impact on the network."

About half of the target area along Mount Gawler Road has been searched with packages of drugs buried close to the surface under trees.

A further two kilometres of roadside will be searched in the coming days.