Traffic is blocked on the A11 near Mildenhall after four vehicles collided at Chalk Hill.
Suffolk Constabulary received reports that three cars and a van had been involved in an accident at about 4.40pm.
Police, ambulance and the fire service were called to the scene, which is currently blocked by the vehicles.
A diesel spillage has covered both carriageways and a diversion is in place along the B1085.
No life-threatening have been reported although firefighters were required to cut someone free from wreckage and at least one of the casualties has suffered a cut to the head.
Police are advising motorists to seek alternative routes where possible, the Jeep Cheroke, Seat Ibiza, Vauxhall Astra and Man box van are removed from the road and the diesel is cleared.
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