Two more people have been arrested after a teenager was stabbed in the chest and legs.
The 16-year-old boy was found injured at a house in Chatham Place, Preston, at about 17:40 GMT on Wednesday.
He was taken to hospital where he remains critically ill with his family by his bedside, Lancashire Police said.
A man, 20, and a 28-year-old woman, both from Preston, have been arrested on suspicion of assisting an offender and are currently in custody.
Police have been given more time to question three teenagers, aged between 16 and 18, who were detained on Thursday.
A 36-year-old woman from Leyland, who was held on suspicion of assisting an offender, has been released while inquiries continue.
Det Ch Insp Lee Wilson said: “This incident has left a teenage boy battling for his life and my thoughts are with him and his family at this extremely distressing time.
“This appears to have been an attack on a defenceless young man and while we remain open-minded as to why this has happened, I want to appeal to the community of Preston and, in particular Deepdale, to come forward if they have any information that could assist us in bringing those responsible to justice.”