Three people have been killed and a fourth person is in hospital with life-threatening injuries following a crash involving a Mondeo, a minibus and a lorry on the M25 near Waltham Abbey.
The motorway remains closed anti-clockwise between junctions 26 and 27 with emergency services at the scene.
East of England Ambulance Service said it was treating a number of people involved.
Police said the road would remain closed for hours.
Tragically, three people have been killed and a fourth person remains in hospital with life-threatening injuries.
We are working to inform their loved ones at this time and we would urge that, out of respect for the families, there is no speculation in the meantime.
Our officers were called to the scene, just outside Waltham Abbey, shortly before 6.15pm this evening, Monday 23 August.
The anti-clockwise carriageway remains closed between Junctions 27 and 26 whilst we continue our investigation and we would urge anyone with information or dash cam footage to come forward.
We are particularly keen to trace the movements of all three vehicles – a Mondeo, a minibus and a lorry – leading up to the collision.
Anyone with information who has not yet spoken to our officers is urged to do so.
Detective Sergeant Steve Holmes, from our Serious Collision Investigation Unit, spoke from the scene to thank those who had assisted officers in the investigation so far.
He said: “This evening has been incredibly challenging and we are continuing to work as quickly as we can to piece together exactly what led to this tragic incident.
“My thoughts, and those of all officers on scene are with the families of those who lost their lives this evening.
“At present, two drivers have been arrested on suspicion of causing death by dangerous driving and on suspicion of causing serious injury by dangerous driving.
“I need anyone with further information to come forward.
“The road has remain closed whilst our colleagues tended to those who were injured and whilst we have gathered evidence and preserved the crime scene.
“I would like to thank everyone on the M25 for their patience – I know it’s been a long night, and our colleagues in Highways England are aiming to get you off of the motorway by 2am.
“Please make sure you get home safely and, if you have any information at all that can help us, don’t hesitate to report it.”
Anyone who witnessed the collision, has dash cam footage, or has information on it should submit a report online at https://www.essex.police.uk or use the ‘Live Chat’ button to speak to an online operator between 7am-11pm.
You can also call us on 101 and cite incident 972 of Monday 23 August.
Information can also be given to independent charity Crimestoppers anonymously on 0800 555 111 or https://crimestoppers-uk.org.