Officers seized more than 300 cannabis plants which have been valued at more than £400,000.
Police in Hartlepool discovered the drugs during a raid at a house in Stockton Road on Wednesday 1 November.
Six people have been arrested on suspicion of conspiracy to produce cannabis.
A 30-year-old woman, a 33-year-old man, 34-year-old man, two men aged 35 and a 48-year-old man were taken into police custody for questioning.
Inspector Adrian Dack, of the Hartlepool Neighbourhood Policing Team said: "It's a fantastic result, to seize cannabis of this value and remove it from trade on the streets of our town.
"Operation Sycamore is an intelligence-led operation, aimed at targeting those producing and dealing drugs in Hartlepool, and making our communities a safer place to live.
"We welcome information from the public, and anyone who suspects drug activity can let us know about it by calling 101."
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