A street in West Cornwall had to be closed off after workers discovered a five-metre deep mineshaft.
Engineering staff at Cormac Solutions Ltd have been clearing silt from a quarter-mile adit that runs along New Street, Laity Road and Treslothan Road, in the village of Troon, near Camborne, down to a nearby stream.
Sharon Sutton, sub-agent with Cormac, said: "Many wrongly thought that the road had opened up," she said, "but we found the shaft while we were working on the adit and excavated it during our investigations."
A concrete chamber is being laid onto the adit's granite foundations to strengthen the shaft before it is covered.
Two terraced cottages on New Street were abandoned a decade ago when water from the adit burst through the ground floor, making the homes uninhabitable. The houses suffered subsidence and are supported by a large steel frame.