All emergency services were called to the incident shortly after 8.20am on Friday 3 November after reports of a vehicle colliding with two children.
Despite all efforts from medics at the scene, one of those children, a boy, has died.
The second child has been taken to hospital for treatment.
A 23-year-old man has been arrested on suspicion of causing death by dangerous driving, causing serious injury by dangerous driving and driving whilst unfit through drink or drugs. He remains in custody.
The road remains closed between School Lane and Honeypot Lane and will remain closed for some time as our investigation into the incident is progressed.
Detective Inspector Mark Fraser, of our serious collision investigation unit, is leading the investigation.
He said: “This is quite clearly an incredibly tragic incident which will be felt by many people across the area, not least the families of the two young victims.
“Our role is to establish the circumstances which led up to this incident, which we will do meticulously and I would ask people not to speculate, whether in person or online.
“I would also like to thank everyone who has already come forward to speak to us and would urge anyone who has information and not yet spoken to us to please come forward.”
We need anyone who witnessed the incident, has dash cam footage of it or has any information to get in touch.
You can let us know by submitting a report on our website or by using our online Live Chat service available Monday to Friday (excluding public holidays) between 10am-9pm.
Visit www.essex.police.uk/digital101 to find out more about our website reporting services.
Alternatively, you can call us on 101.
Please cite crime incident 218 of 3 November.
