The road was shut on the clockwise carriageway, and emergency services were reportedly at the scene.
A statement from Essex Country Fire and Rescue Service said: “Firefighters were called to a road traffic collision on the M25 at Grays between Junction 29-30 at 9:15am.
“Emergency services are on scene with traffic officers deployed to assist.
“Please take care whilst passing the scene in lane 4.
“Road users are advised to allow extra journey time.
“If the lane closures impact on your planned route you may wish to re-route or even delay your journey.”