The B3274 near St Austell is closed in both directions after a wall collapsed overnight - blocking the carriageway completely.
Around a hundred tonnes of debris was strewn across the road.
The road closure will remain in place for the foreseeable as structural surveys will need to be completed.
CORMAC structural engineers have been on site this morning to assess the impact and damage to the highway.
They say "We are working with the landowner and his insurers to consider their proposals for making the remaining wall safe and then to remove the debris off the highway."
The road will remain closed for the foreseeable future until the works are complete to make the area safe. Appropriate diversions are being set up to direct traffic around the area.
How to avoid the road
- Traffic to St Austell travelling south should use the A391 from Stenalees roundabout via the new road at Carluddon.
- Traffic from St Austell travelling northwards towards Bugle and Roche will need to use the A391.
A woman and baby have been taken to hospital after the car they were travelling in crashed into a house in St Austell. It's thought the injuries are not life threatening
It happened on Carwollen Road around lunchtime today and it's thought no one was in the house at the time.
The collision caused a gas leak and engineers were called in to deal with the problem and remove the car.
Chancellor George Osborne met apprentices during a trip to a mechanic's shop in St Austell this morning.
He's claimed to have fixed the economy, but can he fix a car?
The Government's Culture, Media and Sport Committee will be at the Eden Project later as part of a study into tourism.
Representatives will take a tour around the project before meeting key figures in the industry. The aim of the visit is to encourage tourism outside London - and discuss the future of the industry in Cornwall.
A large whale has been washed up on the south Cornwall coastline. The 8 meter whale, thought to be a Minke whale was found dead on Pentewan beach near St Austell this morning. Marine Life Rescue experts say they believe it had been dead for some time.
Plans to landscape an iconic landmark in St Austell to make way for a proposed eco town have been greeted with anger and sadness among residents. They say 'Sky Tip' is a symbol of the town's rich mining heritage but developers want to build 1,500 news homes on it. Planning permission isn't expected to be applied for until 2015.
An iconic landmark in St Austell could be flattened if proposals for a new eco town go ahead. Residents say 'Sky Tip' is a symbol of the town's rich mining heritage but developers want to build 1500 news homes on it. A campaign has started amongst local residents to save it.
Police are asking for the public’s help to trace a 63-year-old man missing from St Austell.
Officers say they are 'extremely concerned' for the welfare of Terence Webb, who was last seen at his home address around 1pm yesterday.
Terence is described as a white male, 6ft tall, heavy build with grey collar length hair and was wearing glasses.
He is clean shaven and is believed to be wearing a navy blue thin raincoat, black fleece and navy trousers.
Anyone who sees Terence or knows of his whereabouts is asked to contact police on 101, quoting log number 734 of 12/07/14.