Thirteen people have been arrested and 28 suspected pit bull terriers seized by police on Merseyside.
Ellie Lawrenson was mauled to death on New Year's Day
The dogs were taken during raids at 16 addresses in the Huyton and Stockbridge Village areas. Nine men and four women, aged between 20 and 53, were held.
Police said the animals were seized under the Dangerous Dogs Act following concerns about organised dog fighting.
The operation was not a direct response to the death of Ellie Lawrenson, who was killed by a dog in St Helens.
Merseyside Police said the raids had been planned for about three months, before the five-year-old was mauled by a pit bull terrier-type dog.
About 60 police officers and 30 RSPCA officers were involved in the operation, which was responding to tip-offs from the community.
Officers arrested four men and three women, aged between 22 and 53 years old, on suspicion of possession of controlled drugs and dangerous dogs.
Two men, aged 18 and 19, were arrested on suspicion of section 18 wounding and a further two, aged 20 and 36, on suspicion of possession of controlled drugs.
A 22-year-old man was arrested on suspicion of possession of controlled drugs and offences related to dog fighting, while a 38-year-old woman was arrested on suspicion of theft.
Merseyside Police said they were continuing to work with local communities and partner agencies to gather information on dangerous dogs.
Supt Dave Connor said: "This is not a problem specific to Merseyside and it is clear that some people keep pit bull terriers as a status symbol.
"They may not fully understand the implications of owning this type of dog.
Owners can be fined up to £5,000 or face a prison sentence
"Dog fighting is a barbaric activity and it will not be tolerated. Anyone who trains or breeds animals for that purpose can expect to be dealt with robustly."
The RSPCA estimates there may be about 100 people involved in "hardcore" underground dog-fighting in Britain.
The sport was banned 170 years ago.
Under the Dangerous Dogs Act 1991, four types of animal are banned - pit bull terriers, the Japanese Tosa, the Dogo Argentino and the Fila Brazileiro.
A person convicted of owning a prohibited dog can face a £5,000 fine or six months in prison.
Anyone with concerns about dangerous dogs which are being kept in their neighbourhoods are urged to contact Merseyside Police or the council dog wardens.