Six of 11 puppies found crammed into plastic bags and a guinea pig cage in a van last month have died from a highly contagious virus, the RSPCA has said.
Police found the young dogs in an “appalling state” after a tip-off from a member of public in Carlton, Nottinghamshire, on 2 March.
The charity said six had since died from parvovirus, despite emergency veterinary treatment.
Two others survived the virus and vets stopped the other three falling ill.
The 11 puppies – aged between two and four months – were found by officers following a tip-off about a smell coming from a house in Apple Walk.
No dogs were found inside the property but officers discovered the “very poorly” puppies in a steamed-up van nearby.
One died the following day and five more have died since.
Nottinghamshire Police said a 20-year-old man who was arrested on suspicion of theft and fraud had been released while investigations continue.
Parvovirus is a highly contagious condition that attacks cells in a dog’s intestines, stopping it from absorbing nutrients and causing weakness and dehydration.
The condition can spread easily through unvaccinated dogs.
The RSPCA said it believed the puppies had been brought from Ireland to Nottingham to be sold.
It has urged the government to crack down on puppy imports after a surge in the number of dogs being brought to the UK since the start of the pandemic.
‘Just too much’
RSPCA manager Ella Carpenter said: “It was heartbreaking to see the puppies fall so ill so quickly.
“They were fighting for their little lives and sadly for six of them it was just too much.”
Two cocker spaniels survived the virus after receiving emergency treatment and three Yorkies were given preventative care.
Four of the five had since been rehomed.