A fire broke out at a house after tenders of a cannabis farm overloaded the plug sockets to keep it illuminated.
When police arrived to the blaze they found the address was empty, but about 70 plants were seized along with growing equipment.
A dog had been left behind which had an injury to its tail and smoke inhalation, so it was taken to an animal shelter.
Fire crews and police officers were called to the blaze on Derby Street in Ormskirk on Friday, just before 1pm.
Initially, it was reported to emergency services that people were still inside the property, opposite the town's railway station, as the flames burned.
The fire was coming from an upstairs bedroom, police said, and was later brought under control by crews.
Two upper rooms suffered fire and smoke damage, it was added.
Cannabis plants were discovered in the cellar of the house.
A spokesman for Lancashire Police said: "We were called to a fire at an address on Derby Street, Ormskirk.
"The blaze was started by overloading plug sockets to illuminate the cannabis farm inside.
"Seventy cannabis plants were seized along with a number of other items.
"Enquiries are ongoing to trace the tenant but thankfully the dog from the address was recovered with only very minor injuries."
Cannabis factories have been regularly uncovered across Merseyside during lockdown.
In May, a significant grow consisting of more than 500 plants straddling two neighbouring flats was uncovered on Aigburth Road - leading to men jumping through windows and scaling walls.
That seizure mirrored a similar discovery when another cannabis cultivation complex was found at an address on Osborne Road in Tuebrook.
The operation involved a growing scheme extending across seven rooms and three floors.
At the start of May, police told how as many as 3,000 plants have been found in the previous six weeks alone, double the figure over the same period last year.
In April, police busted one cannabis farm chanced upon a second - in the house next door.
Officers searched a house on Edge Lane Drive, Wavertree, which revealed a large cannabis farm housing about 175 plants, spread across three bedrooms and in the attic, worth about £700,000.
As police were finishing the search, they noticed the upper bedroom windows of a neighbouring house had been boarded up.
Top news stories
They knocked on the neighbour’s door and, after a search, found another cannabis farm.
Matt Brown, in charge of Merseyside Police's cannabis dismantling team, has warned about "grows" which "have the potential to cause significant harm in the community, whether by the fire and flood risk these farms create, or the serious violent crime they attract."
