A famous Banksy artwork satirising government surveillance was destroyed during work to protect the listed building it was painted on, a council has confirmed.
The Spy Booth mural showed three 1950s-style agents, wearing brown trench coats and trilby hats, using devices to tap into conversations at a telephone box.
It appeared overnight in April 2014 on the wall of a house in Cheltenham, Gloucestershire, just a few miles from GCHQ where the UK's surveillance network is based.
But the wall has mysteriously been stripped back to the brickwork, with photos show rubble lying on the ground around the phone box, which was central to the piece.
A video posted on Twitter on Saturday appeared to show the site covered with a tarpaulin and the sound of machinery on masonry.
Cheltenham Borough Council met with the owner of the property, 159 Fairview Road, on Monday, and confirmed the mural was damaged during repair work to the building, a Grade II listed Georgian end-of-terrace home.
Mark Nelson, built environment enforcement manager at the council, said: "He was carrying out works to his property following an urgent works notice issued by the council to stop further deterioration of the listed building, make it weatherproof and secure the safety of the public by removing the risk of falling render.
"We have endeavoured to protect the Banksy as much as possible and to this end the notice required the owner to have due regard for the Banksy mural whilst works were being undertaken.
"We were aware of loose render on that part of the building where this was situated but the extent and how far it would affect the mural was unknown until work progressed."
Mr Nelson said the property's owner has left pieces of the rendering that form part of the artwork with the council while investigations into how it came down continue.
He said: "We would advise anyone against removing any further pieces from the location as this may be classed as a criminal offence. Until the investigation is complete we are unable to say what if any further action will be taken."
Cheltenham MP Alex Chalk said the artwork was a valued part of the town's heritage and questioned why conservation work may have gone wrong.
He said: "This is absolutely shocking news. The Banksy mural is a much admired piece of Cheltenham's artistic heritage.
"We need an urgent inquiry to get to the bottom of what happened. Whoever is responsible needs to be held to account.''
He added: "We need answers. Has it definitely been destroyed? If so, who by? How did the conservation effort go so badly wrong? Time for urgent clarification."
The mural had been repeatedly subjected to vandalism since being painted on the home, which went on the market in January this year for £210,000.
In February 2015 Cheltenham Borough Council granted retrospective planning permission - meaning it cannot be removed without the approval of councillors.