Emergency services have ruled out that anyone was trapped after searching hundreds of tonnes of rubble collapsed at Lewes Castle.
A search operation got underway on Monday after a wall of the 11th-century fortification fell onto a home in the East Sussex town.
After it concluded, firefighters confirmed on Tuesday that no one had been injured in the incident.
East Sussex Fire and Rescue Service incident commander Matt Lloyd said: "This has been a very complex and unusual situation which has required co-operation and assistance from a significant number of our partners.
"We would like to thank all those involved in this incident, and the public for their patience."
In a Facebook post, East Sussex Fire and Rescue said: "Three search dogs which were deployed at the scene have checked the area.
"Cameras are also being used to look through windows, up stairwells and into voids. No casualties have been found.
"The Service is now helping provide information to structural engineers so that the building can be shored up."
