Five males including three children were killed on Saturday night in Leeds when a stolen car collided with a tree.
Police were called to Stonegate Road in the Meanwood area of the city at 9.54pm on Saturday where the Renault Clio crashed.
A 12-year-old, two 15-year-olds, a 24-year-old and a 28-year-old died in the smash, West Yorkshire Police said, while two 15-year-olds are in police custody.
The families of the deceased have all been informed, investigators said.
Stonegate Road remains closed while the major collision enquiry team investigates the cause of the accident.
A spokesman for West Yorkshire Police said officers were confronted by a scene of “complete carnage” when they arrived at the crash site on Stonegate Road.
He said that just one vehicle had been involved but it was not yet clear whether the five victims and two suspects had all been in the car.
“Whether they were all in the car or whether some of [the victims] were pedestrians we can’t say at this point in time.
“We’ve got the road closed, an investigation in place and we’re trying to find out what’s occurred.”
Detective Chief Inspector Jim Griffiths, who is leading the investigation, said: “This is clearly a tragic incident in which five young people have lost their lives. We are currently investigating the exact circumstances of what happened.
“I would like to take this opportunity to ask anyone who saw what happened or has information about it to call us on 101 quoting log 1859 of Saturday 26 November.”
The car had been removed from the scene of the crash by mid-morning.
A large scar could be seen on the tree, which is about 150m behind a cordon.
Around a quarter of a mile section of the leafy suburban road continued to be sealed off by the police, with officers guarding a number of intersections and police vans being used to enforce the cordon.
The street, which is about three miles north of Leeds city centre, has semi-detached houses on one side and wide grass verges between the houses and the roads.