East bound A17 closed at Sutton Bridge, Traffic diverted down A1101 to Wisbech.
Part of the A17 will remain closed into the night, with traffic between the East Midlands and Norfolk diverted via Wisbech.
Repairs are being made to the east-bound carriage way at Cross Keys Bridge.
Drivers are being diverted via the A1101 to Wisbech, to cross the nene at Freedom Bridge, and the A47 to King's Lynn.
Fire crews from Long Sutton, Terrington St Clement, King's Lynn and Swaffham were sent to the fire, near the power Station. No-one was injured.
The wreckage of the crane was removed but police said it was not clear when the road would re-open.