Repairs to the A30 at Sherborne will enter a third week after additional damage has been identified.
The road has been closed in both directions between Marston Road and Bristol Road and has been since last Thursday, August 11.
It will now remain closed until "mid-week".
As reported, a combine harvester collided with a raised walkway on Greenhill which contains a gas line, and damaged the link in two different places.
SGN - which looks after the gas network - has made Dorset Council aware of additional damage to their gas mains within the section of the road that is closed.
It will make these repairs now to avoid having to return in future, and so the road will remain closed.
Speaking earlier in the week, a spokesperson for Dorset Council said: "The repair is complex with some of the damaged apparatus no longer meeting required standards."
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