The A11 at Barton Mills has been closed in both directions after a power cable came down.
Suffolk police were called at 10.50am to the stretch of road near the Fiveways roundabout.
A police spokeswoman said power cables on the southbound carriageway had fallen, and had caused a blockage to the road in both directions.
Officers have closed the road in both directions while work is underway.
UK power Networks have been called and are due to be on scene shortly.
Motorists are being advised to avoid the area while work is ongoing to clear the lines.
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