Sydney cannabis crop uncovered in blaze

First responders to a home on fire in Sydney's west have discovered a cannabis crop growing inside.

An extensive indoor cannabis crop has been uncovered after emergency services responded to a house fire in Sydney's west.

Firefighters extinguished a blaze at the property at Marayong at 6.30pm on Sunday and then discovered more than 250 cannabis plants growing in an indoor hydroponic system.

Police have placed a guard at the home as they work to identify who was renting the house.