Two brothers were stabbed to death after a gang of men attacked their van in south-west London.
The brothers were sitting in a van when a group attacked them
Mohammad and Hayder Ali, aged 23 and 24, were found fatally wounded outside a house in Fircroft Road, Tooting, on Saturday. Both later died in hospital.
They were attacked by a gang of up to 15 men, who smashed the van's windows. The two then either climbed out or were dragged out, before being stabbed.
Three of the seven men arrested over the deaths have been released on bail.
Knives and baseball bats
A third man, who was in the driver's seat throughout the attack, was unharmed.
Mohammad, from Battersea, south London and Hayder, of Southfields, south-west London, were attacked at the junction of Fircroft Road and Tooting High Street at about 0016 BST on Saturday.
Police said a large number of weapons, including knives and baseball bats, were being examined by forensic experts.
Det Ch Insp Mick Duthie said: "At this early stage of the investigation we are keeping an open mind as to why one group of Asian men attacked another.
"This attack on two young men has resulted in a family losing not one, but two sons."
He appealed to the local community and anyone who has information to help catch those responsible.
Roads surrounding Upper Tooting Road were sealed off as officers carried out forensic examinations.