Thirteen people are being held in custody after a 19-year-old student was shot dead in the street as she walked to a Lidl supermarket.
Police said they have been “working round the clock” to find out who killed Aya Hachem in a drive-by shooting in Blackburn on Sunday.
Miss Hachem, described by her family as “the most loyal, devoted daughter”, was an innocent bystander who was hit by one of several shots fired from a vehicle as she walked to a Lidl supermarket near her home, Lancashire Police said.
She died from a single wound to the chest.
Detectives have been granted extra time by magistrates to continue questioning three men, aged 33, 36 and 39, all from Blackburn, on suspicion of her murder after their arrests on Monday.
On Wednesday, police said they had made eight more arrests.
Three men aged 28, 31 and 35 were held on suspicion of murder and two women aged 19 and 26 and a 29-year-old man were detained on suspicion of assisting an offender.
And a further two people – a 29-year-old woman and a 39-year-old man – were arrested on Wednesday afternoon.
Two more men, aged 34 and 24, were arrested on suspicion of murder on Thursday, police said, taking the total number in custody to 13.
Police believe Miss Hachem was not the intended target of the attack, which took place in broad daylight on a busy main road near a Lidl supermarket in the town centre.
The Lebanese-born teenager died in hospital a short time after emergency services were called to the scene in King Street at around 3pm.
Senior Investigating Officer, Det Supt Andy Cribbin, said: “This is a very fast moving investigation, with information coming in from various places which we are reacting to swiftly.
“I continue to appeal to people who think they know who was involved in the tragic shooting of Aya but haven’t spoken to us yet to do the right thing and make contact.
“Aya, the innocent victim in all of this, along with her family, deserve justice and it is people telling us what they know that will help us find the people or person responsible.”
Miss Hachem’s family described her as “the most loyal, devoted daughter” who died in the “most horrific circumstances”.
“She excelled in her studies both at Blackburn Central High School and at Salford University where she was in her second year and dreamed of becoming a solicitor,” her family said in a statement.
“She had just completed her exams and was learning to drive.
“We her parents are absolutely devastated by her death and would like to take this opportunity to plead with any members of the public who may have any information however small that may bring those responsible to justice.”
Anybody with information should contact 101, quoting log number 0412 of May 18, or anonymously via Crimestoppers on 0800 555 111.