Officers were called to reports of a fight between people in two vehicles involved in a crash in Watford Road at 2.10pm yesterday (February 18).
By the time police arrived, everyone had reportedly left the scene.
Shortly after, a man attended hospital with stab injuries who remains there receiving treatment.
His injuries were assessed as non-life threatening.
No arrests have been made as police enquiries continue.
A spokesperson for Metropolitan Police said: “Police were called at approximately 14:10hrs on Tuesday, 18 February to reports of a fight involving the occupants of two vehicles that had been involved in a collision in Watford Road, Harrow.
“Officers attended the scene but all parties had left. Road closures remain in place while the scene is dealt with.
“A man subsequently attended hospital with stab injuries. He remains there receiving treatment. It does not appear that his injuries are life threatening.
“Enquiries are ongoing to locate others involved.
“There have been no arrested. Enquiries continue.
“Anyone with information that could assist police is asked to call 101 or ‘X’ @MetCC and quote CAD 3800/18Feb.
“You can also provide information anonymously to the independent charity Crimestoppers on 0800 555 111.”
