A vast carpet of more than 100 million porcelain "seeds" in the Tate Modern has been declared out of bounds to art lovers only two days after it opened because it poses a health threat.
Visitors to the London gallery were initially allowed to walk on the imitation sunflower seeds, which cover 1,000 square metres of its Turbine Hall, but that has now changed.
A Tate spokeswoman said: "Although porcelain is very robust, the enthusiastic interaction of visitors has resulted in a greater than expected level of dust in the Turbine Hall. Tate has been advised that this dust could be damaging to health following repeated inhalation over a long period of time. In consequence, Tate, in consultation with the artist, has decided not to allow visitors to walk across the sculpture."
The seeds, which were individually handcrafted by skilled artisans, are the idea of Chinese artist Ai Weiwei.
The ceramic seeds were moulded, fired at soaring temperatures, hand-painted and then fired again over the course of two years.
Sunflower seeds are a popular Chinese street snack but also hold another meaning for the artist, political dissident in China.
During the Cultural Revolution, propaganda images showed Chairman Mao as the sun and the mass of people as sunflowers turning towards him.
The seeds are the latest instalment in The Unilever Series which was launched in 2000 and has included Doris Salcedo's split of the floor of Tate Modern, Carsten Holler's spiralling slides and the popular Weather Project.
The exhibition opened to the public on Tuesday before being closed on Thursday, but can be viewed from a bridge in the gallery.
It is not the first time the Tate has run into trouble over an installation in the hall.
Three visitors lost their footing and fell into the gap in the floor when it was installed in 2007.
Last year a visitor was injured after wandering into the "black hole" exhibition on the first day it opened to the public.
Titled How It Is, the work by Polish artist Miroslaw Balka allowed people to enter a huge steel chamber into a void of pitch-black darkness.
The gallery's statement comes on the day the Government pledged to tackle the UK's "damaging" compensation culture with a shake-up of health and safety measures and an end to "senseless" rules and regulations.
Prime Minister David Cameron said he hoped a review carried out by former Conservative minister Lord Young would prove to be a "turning point", with a new system being introduced to replace "unnecessary bureaucracy".
Mr Cameron, in a foreword to the report, said the Government would introduce a new system that "treats adults like adults".Reuse content