Residents say a road where a toddler and his sister were critically injured in a hit and run collision is used as a "drag strip" by boy racers.
Raham Saleem, two, and his ten-year-old sister Sabam were knocked down while crossing the road with another youngster near the Makkah Masjid Mosque in Leeds.
Police urged the driver of a silver Vauxhall Astra to come forward after the crash in Brudenell Road, Hyde Park, at around 5.20pm on Saturday.
Raham and Sabam were taken to Leeds General Infirmary and remain in a critical condition following surgery.
Witness Inzimaam Sulman, 12, who knew the children, told Sky News: "I was playing in my bedroom and I heard a car driving really fast up the road.
"I looked out of the window and I saw the children walking across the street with a bag of onions and the car just smashed into them. They were flown into the air.
"I couldn't believe it. It was awful. I went outside and I could see their mum and dad on the road. It was horrible."
His father, Manover Sulman, told Sky his street was being used as a "drag strip" by young drivers.
"They drive 50mph up this street because it's long. They use it for drag racing. It's terrible. It has been going on for a while now and nothing seems to be done about it.
"There are speed bumps, but they don't make any difference."
Mr Sulman said he saw a silver Vauxhall Astra, similar to the one police are looking for, driving at speed up his street on the day the children were knocked over.
Police are studying CCTV footage of the incident.
Detective Superintendent Paul Taylor, leading the investigation, said: "Wide-ranging inquiries by detectives and specialist officers are under way to trace the driver of this car.
"I would urge that driver to come forward and contact us now before they receive a knock on the door."
He added: "The family of these youngsters are understandably extremely distressed and for their sake we are keen to trace this driver as soon as possible."
:: Anyone with information can call Crimestoppers on 0800 555 111.