A section of the ancient walls around the city of Chester has collapsed after development work.
A spokesman for Cheshire West and Chester Council said part of the city walls, which were built by the Romans, collapsed on Thursday night after excavations carried out by a private developer "compromised the integrity of the ancient monument".
No one was injured as a result of the collapse and investigations are under way to establish the exact cause.
The council spokesman said early indications appeared to show earth had been removed from the bottom of the walls and exposed a section of bare foundations.
The developer has now stopped work within the site at the back of the Grosvenor Shopping Centre, adjacent to the Wesley Church Centre in St John Street, which is alongside the walls, to allow assessments to be done, the spokesman said.
It is very close to the 30-metre section of the walls, parts of which date to medieval and Roman times, collapsed nearby in April 2008, adjacent to the Grosvenor Hotel. Again nobody was hurt.
Deputy council leader Councillor Karen Shore said: "The council is taking this situation very seriously and we will ensure that a thorough investigation is carried out.
"I am thankful that no-one has been hurt as a result of this collapse and our priority will continue to be public safety."
The earliest surviving sections of the wall date back to 120AD.
The walls are also famous for archaic by-law which states any Welshman loitering within the city walls after sunset may be killed by decapitation or shot with a longbow.
