Abigaile Muamba, 31, from Edmonton Green, north London, 60-year-old Dexter Augustus, from Waltham Forest, northeast London, and 59-year-old Jennifer Smith, from Stratford, east London, died at the scene.
And the latest victim has been named as 44-year-old Lisa Gardiner, from Walthamstow, east London.
Police are now investigating the crash, Essex Live says.
Inspector Mark Fraser, who leads Essex Police’s Serious Collision Investigation Unit, said: “Our thoughts are with the families and loved ones of those who lost their lives in this awful incident.
“My officers are working tirelessly to try and piece up what led to the collision.
“If you saw the three vehicles prior to the collision – a Mondeo, a minibus and a lorry – or have any dashcam of their movements, please contact us.
“Four people have lost their lives and we need to get to the bottom of what happened.”
Two men were arrested that evening, the minibus driver and a lorry driver. However, the minibus driver has since been de-arrested following new information.
The lorry driver, a 64-year-old man from Ipswich, Suffolk, was arrested on suspicion of causing death by dangerous driving, causing serious injury by dangerous driving, and driving whilst unfit through drink or drugs.
Anyone who witnessed the collision, has dashcam footage, or has information on it should submit a report online or use the ‘Live Chat’ button at essex.police.uk to speak to an online operator between 7am-11pm.
You can also call Essex Police on 101 and cite incident 972 of Monday 23 August.
Information can also be given to independent charity Crimestoppers anonymously on 0800 555 111.