We have sent two ambulances, a rapid response vehicle, our hazardous area response team and Hertfordshire Air Ambulance to the scene of a several vehicle collision between junctions nine and eight of the M11 northbound.
Police have closed the motorway in order to allow the air ambulance to land.
More top news
Paramedics were on standby outside the police cordon as armed officers stood by the property.
A team of researchers has taken samples from the ten busiest London Underground lines to work out which are the dirtiest.
The action comes on top of an emergency timetable which has seen hundreds of trains a day being axed.