Police were called on Monday shortly after 6:50 p.m. at East India Dock Road in Poplar, where a child reportedly “fell from a height”.
They were treated at the scene by paramedics before being taken to a large trauma center, the London Ambulance Service (LAS) said.
An air ambulance also attended the scene.
The child was then transferred to a specialized hospital and is in critical but stable condition, police say.
A spokesman for the Metropolitan Police said no arrests had been made.
The road was closed at the junction with Chrisp Street and Newby Place at 8:30 p.m. Monday.
Those who witnessed the incident or have images are urged to contact the Met citing CAD reference 6419/27 July.