Surrey Police say the collision happened at 8.32am at junction 13 for Staines and involved two heavy goods vehicles on the anti-clockwise carriageway.
Both carriageways were closed for a short period to allow an air ambulance to land and then take off again following the driver of the lorry being freed.
One lane of the anti-clockwise carriageway has opened to free trapped traffic, however other lanes remain closed and and are likely to be so for some time while officers carry out their investigation.
Full diversion information can be found here: https://m.highwaysengland.co.uk/#news.
Anyone who witnessed the collision or who may have dashcam footage is asked to contact Surrey Police on 101 or tell them online via or http://surrey.police.uk/TellUsMore quoting reference PR/P19040319.
You can also give information, 100% anonymously, to the independent charity Crimestoppers on 0800 555 111; or through their anonymous online form: https://crimestoppers-uk.org/