One of the region's busiest roads was closed yesterday after a giant hole opened up - and it is feared a whole network of old mines could lie underneath.
The A30 was closed at Scorrier, near Redruth, after a hole believed to be 25ft deep opened up alongside the carriageway at around 1pm.
Traffic was diverted while a team from the Highways Agency investigated.
A spokesman for the organisation said it was hoped that one lane would reopen at around 6.15pm.
"Our priority is safety, but we are also working very hard to get part of the road reopened," she said.
An investigation is under way to determine the cause of the hole, which opened on a verge alongside the carriageway.
It is thought it might have something to do with the extensive network of mineworkings which run underneath the area and are often blamed for subsidence.
The Highways Agency spokeswoman said they had a mining engineer at the scene, but were unable to say what caused the hole.
"An investigation is ongoing," she said.
Traffic has been diverted around the area and was reported as very heavy around Chiverton Cross, near Truro.
