The A143 south of Bury St Edmunds has been closed in both directions following a crash between three cars.
The road has been shut between Chedburgh and Whepstead, Suffolk police said on Twitter on Wednesday morning.
Officers are currently at the scene, while fire crews from Bury St Edmunds and Wickhambrook stations were dispatched earlier in the morning.
A spokesman for Suffolk police confirmed a BMW, Citroën and Land Rover were involved in the crash.
The police spokesman later confirmed that a man had been taken to Addenbrooke's Hospital in Cambridge with suspected life-changing injuries.
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