The incident happened between junctions 22 (London Colney) and 21A (North Orbital Road/St Albans) at around 4am.
Four vehicles were involved – a white Citroen Dispatch van, a silver DFSK 580 Glory, a silver Skoda Superb and a black Peugeot 5008.
Two people sadly died and their families are being supported by specially trained officers.
A man in his twenties has been arrested on suspicion of causing death by dangerous driving.
Officers in a marked vehicle had been in pursuit of the van shortly before the collision.
The pursuit was quickly abandoned as the officers assessed that the risk of continuing was too high.
As a matter of course, the incident was referred to the Independent Office for Police Conduct who are now investigating and Essex Police are conducting a criminal investigation into the collision.
Detective Inspector Mark Fraser, from Essex Police, said: “Our thoughts are with the loved ones of those who lost their lives in this collision.
“I am appealing for any witnesses or anyone with information to get in touch.
“Did you see what happened or the events leading up to the collision? Please don’t hesitate to get in touch if you can help.
“I also want to ask any dashcam owners who were driving in the area to check it and get in touch if you spot something that might help us.
“You can email me at [email protected].”
You can also report information online at herts.police.uk/report, speak to an operator in our Force Communications Room via our online web chat at herts.police.uk/contact or call the non-emergency number 101, quoting Op Sericeous.
Alternatively, you can stay 100% anonymous by contacting the independent charity Crimestoppers on 0800 555 111 or via their untraceable online form (opens in a new window).
