More than $1 million worth of cannabis has been seized during a police raid in Sydney's southwest.

A "sophisticated hydroponic set-up" was used to grow 301 plants found during a search of a Harrington Park home on Tuesday afternoon, police say.

"(The plants) have an estimated potential street value of $1,064,000," police said in a statement.

No one was home when police arrived.

Growing equipment including light bulbs, electrical transformers and filters were also seized and sent for forensic tests.

Police say they are following several leads as they search for the growers.

Late last month about 360 plants, worth $1.2 million, along with hydroponic growing equipment were found by police in a Punchbowl house.