A freak hail shower has led to 13 cars being involved in accidents on the A120.
Police officers have been called to a series of incidents between Braintree and Great Dunmow since 2.30pm.
An Essex Police spokesman said: "At this time there doesn't appear to be any serious injuries."
Two police patrol cars are among those which have crashed.
The East of England Ambulance Service has confirmed it has two ambulances on the scene.
One person was taken to hospital with minor injuries.
Writing on Twitter, Witham resident Keith Windard said: "Don't know how many cars exactly but around nine with the police car.
"Looks like the weather was to blame. Hail was bad, like a sheet of ice.
"I can have only been a minute or two behind from when it happened. Lots of other emergency services were driving from Braintree to the accident."
In the middle of 7 car crash on A120,Sooooo lucky not to hit anything,even the cops crashed! pic.twitter.com/lDPVejEhWS— Mark Hopkinson (@Skidv8) March 3, 2014