Eight pit bull terriers have been seized during police raids in St Helens and Widnes.
The raids followed the death of Ellie Lawrenson, five, who was mauled by a type of pit bull terrier at her grandmother's home on Monday.
Six of the dogs were taken from St Helens, the town where Ellie died. Police suspect they were being trained to take part in dog fighting.
A 23-year-old man has been questioned in connection with Ellie's death.
The man went voluntarily to a police station on Wednesday evening on "matters arising" from the attack that killed Ellie, but was not arrested, Merseyside Police confirmed.
Speaking about the dogs, seized in separate, unrelated raids in St Helens and Cheshire on Thursday, Ch Supt Paul Forrester from Merseyside Police said they needed to establish what type of animals they are.
"They are young dogs, with no visible marks or scars consistent with being in a fight," he said.
"One did have cropped ears but that may be a status symbol for street culture.
"We don't read anything more into that at this stage, we were responding to a call to Crimestoppers."
Post-mortem tests showed the dog that killed Ellie was among the breeds prohibited by the Dangerous Dogs Act.
Pit bulls are one of four breeds banned under the legislation.
Anyone convicted of owning a prohibited dog can face a £5,000 fine or six months in prison under the 1991 Act.
Ellie suffered head and neck injuries
Two previous complaints had been made about the pet, which belonged to Ellie's uncle.
Ellie was staying with her grandmother, Jackie Simpson, while her mother and father went out to celebrate the New Year.
Ms Simpson, 45, suffered arm injuries while trying to get the dog off Ellie. She has undergone surgery at Whiston Hospital.
Police have yet to speak to her about what happened.
The dog was shot dead by a police marksman following the attack.
Floral tributes were laid by members of Ellie's family on Tuesday at the house in which she died.