Two more people were arrested in London this morning on suspicion of the murder of Paul Thrower, 46.
Police are yet to confirm their ages or whether they are male or female.
Three other males, two aged 17 and one aged 18, were arrested in Leeds on Tuesday night and remain in custody at a south London police station.
Borough commander for Hillingdon, detective chief superintendent Steve Kershaw, said: "The investigation is going really well."
A 16-year-old was arrested following the stabbing on Thursday night last week but was bailed until a date in April.
Charges are expected later today.
Mr Thrower died on Thursday night after receiving stab wounds in an altercation at his block of flats in St Dunstans Close in Hayes.
More as we get it.
