The drone's thermal imaging camera detected the cannabis farms at two homes in the St Matthew's area of the city yesterday (Thursday, August 27).
Officers with the Preston task force and tactical ops team raided the properties where they uncovered more than 500 plants at various stages of growth. Some were just weeks away from being ready for sale on the streets.
Two Albanian men in their 20s have been arrested and are awaiting interview by Immigration officers.
A police spokesman said: "Drones thermal camera has uncovered two addresses in the St Matts area used to cultivate cannabis, with over 500 plants inside.
"Two Albanian males in their 20s have been arrested and are awaiting interview by Immigration.
"Anyone with any information please email us directly at: [email protected]"