Two men suffered serious injuries after the lorry they were travelling in crashed near Sawtry.
The Great North Road B1043 and the slip road on to the A1(M) was closed following the crash which was reported at just before 11am yesterday.
One man, a passenger, suffered injuries that were initially described as life threatening but are now deemed serious.
Another male passenger also suffered a serious but not life threatening injury, while the driver, also a man, suffered a slight injury.
Police are investigating the crash and urge anyone who saw what happened to call PC Leigh Fenton, at the road policing unit, on 101.