Essex police have confirmed a 12-year-old boy has died following a collision with a car outside Debden Park High School.
A number of other casualties have been reported but none are believed to be in life-threatening or changing condition.
Other victims include two 15-year-old boys, one 13-year-old boy, one- 16-year-old girl and a 53-year-old woman.
The force have launched a murder probe and are looking for the owner of a silver Ford KA who drove into a group of children in Loughton.
Inspector Rob Brettell of Essex Police Serious Collision Unit said the car in question is "likely to have damage to the front" of it.
He said: "We are trying to locate and find a Silver Ford KA which is likely to have damage to the front of the car."
Essex Police have appealed for anyone with information to contact the force on 101 or by calling Crimestoppers anonymously and quote 726.
The force tweeted: "We are appealing for help to find a silver Ford KA in connection with the collision this afternoon in Willingale Road #Loughton.
"Please help as per below from roads policing Inspector.
"Please do not speculate about those who may be involved.
"We will update when we are able."
Several school children are thought to of been hit by the car outside as school finished today at around 3.30pm.
The vehicle involved in the incident reportedly attempted to drive into children earlier at 3.10pm near Brooke Road - but this has not been confirmed.
Emergency services were called to the incident on Willingale Road near to Debden Park High School and the road was closed in both directions.
An Essex & Hertfordshire Air Ambulance had been spotted landing near the scene and a large police presence still remains.
Detective Chief Inspector Rob Kirby of the Kent and Essex Serious Crime Directorate said: “This has been a truly shocking incident and my deepest sympathies are with all those involved.
“I would like to thank the many members of the public who have called us with information and spoken to our officers, as well as those who provided crucial medical assistance at the scene."
Essex Police are aware of reports surfacing on social media but have urged the public not to speculate on the circumstances of the collision.
Cops said: "We remain at the scene of this collision in #Loughton and the picture is fast-moving.
"We would urge people not to speculate on the circumstances or people involved.
"We must make sure our updates are accurate."