Police have arrested a 40-year-old man in connection with the murder of Olivia Pratt-Korbel.
Nine-year-old Olivia was shot in the chest at her home in Dovecot, Liverpool, on August 22.
Her mother, Cheryl Korbel, 46, was injured as the gunman chased convicted burglar Joseph Nee into their property at about 10pm.
On Friday, Merseyside Police said a 40-year-old man from Dovecot was arrested on suspicion of assisting an offender.
A spokesman said: “He has been taken to a police station for questioning.
“This is the 11th arrest to date.”
Police said on Thursday that a 34-year-old man from Dovecot had been arrested on suspicion of murder. He remains in custody.
Previously, nine men have been detained as part of the investigation and all were later bailed.
The reward offered in the hunt for the killer has been increased to £200,000.
Announcing Crimestoppers’ biggest single reward offer last week, the charity’s founder and chairman Lord Ashcroft said: “This case has been incredibly shocking, not just for those who are directly affected but also for Liverpool and the nation as a whole.
“I am delighted that with the support of a private donor, Crimestoppers can now offer a record £200,000 for information to catch Olivia’s killer.
“A precious young life has been lost so we need every effort to find those involved in this appalling killing.”
Police have also revealed the two weapons used were a .38 revolver – the gun responsible for killing Olivia – and a Glock-type self-loading 9mm pistol which was fired in the initial stages of the incident.
Earlier this month her funeral was held at St Margaret Mary’s Church in Knotty Ash.
Pink ties, jackets, scarves and bows were worn by those attending the service after her family asked people to wear a “splash of pink”.
Ms Korbel carried a pink teddy bear into the service, during which she said: “Liv touched so many people’s hearts and was loved and adored by everyone. She will never be forgotten.
“I will never say goodbye but what I will say is goodnight, love you, see you in the morning.”