Two cannabis factories were discovered inside houses in Wakefield on Sunday after firefighters attended fires at neighbouring properties.
Police were called to West Parade at around 10.52am after firefighters attended a fire at the property.
Between 30 and 40 plants were discovered in the loft of the property.
Also in the news: Fire breaks out at Wakefield house
On Sunday evening, officers attended a property on Berners Street following the discovery of cannabis plants at a property while attending a fire at an adjacent, unoccupied home.
A spokesperson for West Yorkshire Police said: "Anyone who has information about cannabis production on either street is asked to contact the Wakefield Central and North West NPT on 101.
"Information can also be reported anonymously to the independent Crimestoppers charity on 0800 55 111."