Lincolnshire Police said two other people were in the vehicle and were not seriously hurt.
The force said it was keeping an “open mind” over the cause of the collision but said it could be linked to icy conditions in the area. Met Office records show temperatures had fallen to around -2C (28F) at the time of the crash.
The family of the boy is being supported by specially-trained officers.
Alicia Kearns, the Conservative MP for Rutland and Stamford, said the incident was “heart-breaking” and said her “heart goes out to the family and loved ones at this impossible time”.
Lincolnshire Police said it was keen to speak to anyone who may have been driving in the area at the time of the incident or over the past few days.
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