Police officers and London ambulance service (LAS) paramedics attended the scene in Bishopsgate, near Liverpool Street station, on Thursday morning.
Four people were treated at the scene, where witnesses told of seeing a number of men on the ground with bloodied faces. One theory was that someone trying to take a bike had been challenged.
A cordon was in place along the pavement outside a large-scale office, while pieces of emergency medical equipment, scissors and what appeared to bandages lay on the ground, The Guardian reported.
Officers have set up a cordon in the area.
MA/PR