$1.5 million of cannabis in Sydney's west

Cannabis worth $1.5 million has been seized in a western Sydney raid.

Following a tip-off, police searched a commercial premises in Penrith about 6am on Thursday.

They say officers found approximately 500 cannabis plants growing in a set-up spread across six rooms in a large warehouse.

A seventh room served as a seedling nursery.

A sophisticated lighting system and commercial grade air filtration were also part of the set-up.

The raid follows the discovery of $3 million worth of cannabis in Sydney's south on Tuesday.

Fire and Rescue NSW responded to calls of an electrical fire in a building on Forest Road in Bexley on Tuesday night where they discovered an elaborate hydroponic set-up spread across the three-storey premises.

Police seized about 1000 cannabis plants.

Investigations into both discoveries are continuing.