A bag of rubbish that was part of a Tate Britain work of art has been accidentally thrown away by a cleaner.
The bag filled with discarded paper and cardboard was part of a work by Gustav Metzger, said to demonstrate the "finite existence" of art.
It was thrown away by a cleaner at the London gallery, which subsequently retrieved the damaged bag.
The 78-year-old artist replaced it with a new bag. The gallery would not reveal whether he would be compensated.
The bag was part of Metzger's Recreation of First Public Demonstration of Auto-Destructive Art, a copy of a piece he produced in 1960.
Tate Britain said the work "is made up of several elements, one of which is a rubbish bag included by the artist as an integral part of the installation".
"On 30 June, the bag was accidentally removed and damaged but was subsequently replaced."
The gallery said the work is now covered over at night so it cannot be removed again, and staff have been made aware that the rubbish bag is part of the exhibit.
Damien Hirst's 2001 installation was also mistaken for rubbish
Metzger, a German artist who lives in east London, invented "auto-destructive" art in 1959.
The work also features an "acid painting" - nylon covered in acid which slowly destroys it to illustrate the transient nature of paintings, sculptures and other artworks.
It is part of the gallery's Art and the 60s exhibition, which looks at art after 1956 and also includes works by David Hockney and Peter Blake.
It is not the first time such a mistake has been made. In 2001 a cleaner at a London's Eyestorm Gallery gallery cleared away an installation by artist Damien Hirst, having mistaken it for a pile of rubbish.
The collection of beer bottles, coffee cups and overflowing ashtrays was said to represent the chaos of an artist's studio.
And in the 1980s the work of Joseph Beuys, which featured a very dirty bath, was scrubbed clean by a gallery worker in Germany.