Paramedics, firefighters and police were called to a multi-vehicle crash this morning on the M25, near Chorleywood.
Two lanes are closed near Junction 18 and there is queuing traffic after three lorries and two cars crashed.
Hertfordshire Constabulary were called by a member of the public at 9.20am and all traffic on the anticlockwise stretch near Junction 18 is passing through lanes three and four.
A silver BMW 3 Series and a grey Vauxhall Astra Estate are waiting to be recovered.
Firefighters were called to the scene following concerns that people may be trapped in their cars, but so far their assistance has not been needed.
Highways are predicting that traffic conditions will return to normal by 11.30am.
Three people were treated at the scene and two were taken to Watford General Hospital with what are believed to be non-life threatening injuries.