Three men believed to be in their late teens and early 20s have been killed after their car and an articulated lorry collided.
A third person was taken to hospital with serious injuries following the crash on the A10 near Turnford, a spokesman for Hertfordshire Police said.
The accident happened on the northbound carriageway at around 2.15pm when a Vauxhall Corsa collided with the Mercedes Artic lorry.
The driver and two passengers in the Corsa died at the scene while a third passenger was taken to the Royal London Hospital, Whitechapel, by air ambulance with serious injuries.
The driver of the lorry was not injured.
More top news
The Met Police Commissioner admits change is required after a report highlighted failures in the service's conduct in rape investigations
Around 20 cars have been damaged after part of the roof of an Audi showroom collapsed.
Nick Clegg said this was why it was so tragic to see someone with 'such huge gifts' struggle with demons - in Kennedy's case alcohol.