An enormous explosion on the M40 was so loud that nearby residents thought a bomb had gone off when their houses shook.
Reports suggest a crane lorry was involved in the collision with locals reporting as many as five blasts.
“Now hearing it was a vehicle that exploded on the M25 – seems strange though given we heard 4-5 explosions, minutes apart.”
Another added: “5 massive explosions fire and black smoke very nearby. Shook house. Defo not good whatever it is.
Buckinhamshire Fire and Rescue service said there were 35 firefighters and officers at the scene who used foam and hoses to tackle the blaze.
Six fire engines as well as a water tanker and command unit were sent to the incident.
Pictures and video posted from the scene show flames towering from the crane lorry and another vehicle by the verge.
The southbound carriage at Junction 2 is closed and will be for several hours, officials have said.
There are not thought to be any injuries.