Three people have died and two drivers have been arrested after a serious crash on the M25 in Essex.
One person is also in hospital with life-threatening injuries, police said.
The crash, involving a lorry, a minibus and a car, happened near Waltham Abbey at around 6.15pm on Monday.
Two drivers have been arrested on suspicion of causing death and serious injury by dangerous driving.
Essex Police said in a statement the crash happened between junctions 27 and 26 of the anti-clockwise carriageway. Traffic was stopped, causing hours of delays.
Police are investigating the movements of a Ford Mondeo, a minibus and a lorry in the lead up to the incident and are appealing for witnesses.
Detective Sergeant Steve Holmes, from the Serious Collision Investigation Unit, 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.”
Nine ambulances, two air ambulances, several police vehicles and fire engines from Brentwood, Loughton, Waltham Abbey and Epping attended the scene, emergency services said.
It also thanked drivers for their patience.
Parv Domah, who was caught up in the traffic tailbacks near junction 26, said: “I can’t tell you exactly what happened, I can only say I’ve been here going on three hours.
“There were approximately 30 emergency vehicles that drove past in that time, as well as two air ambulances.
“Traffic was stopped on both sides of the carriageway at one point and now on the anti-clockwise is still shut.”
Police are appealing for anyone with dashcam footage to submit a report at essex.police.uk, or call 101 citing incident 972 of August 23.
Information can also be given to Crimestoppers anonymously on 0800 555 111 or crimestoppers-uk.org.