Two cars have crashed into the water-filled ditches which run alongside the a section of the A47 near Great Yarmouth.
Police were called to the Acle Straight at 1.50pm on Thursday to reports of a crash on the busy road.
A police spokesman said both cars were believed to be above the water level.
The ambulance service are on the scene but it is not yet known if anyone was injured.
First Bus, which runs the X1 and X11 route between Norwich and Great Yarmouth via the road, has advised customers to expects delays.
Police have said that traffic is able to move at the moment as both cars are in the dyke.
The crash happened after the Halvergate turn on the Yarmouth-bound carriageway.
Traffic is queuing in both directions.
More to follow.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here