Crash blocks A140 (Image: ©Archant Photographic 2010)
The A11 is closed southbound at Barton Mills just before the Fiveways roundabout after a two vehicle collision.
Suffolk Police have taken the step while they deal with the incident.
Paramedics are treating one female patient at the scene.
Her injuries are not thought to be serious and she is reported to be conscious and breathing.
She was taken by ambulance to West Suffolk Hospital as a precaution.
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