Police in Wyre are investigating after reports of people going door-to-door selling fresh fish - amid fears they are actually dognappers.
A spokesman said: "Reports are these persons are looking at dogs in the properties with a potential intention to take them.
"Please be mindful of this, and if anyone has information or suspects anyone to be acting suspiciously, please call 101."
Dognapping has soared by almost 80 per cent in the past two years in Lancashire, according to the latest police figures.
The shock rise has put the county in the top four for dog thefts in the UK, with illegal puppy breeding and the trade in designer pets offering criminals an increasingly lucrative living. Last year 116 dogs were reported stolen in Lancashire - a 78 per cent increase from 2015.
The numbers were described as 'only the tip of the iceberg' by a volunteer network which helps owners search for their missing pooches.
“We think it’s a lot more than that,” said Jayne Hayes from DogLost UK.
“The figures only refer to those owners who have been able to get a crime number. There are a lot who haven’t.”