A Mark Rothko painting was defaced by a visitor at London's Tate Modern gallery on Sunday said police.
The painting, entitled Black on Maroon, was approached by a man who wrote something in the corner with black marker and then quickly left the museum.
The Telegraph said that the graffiti reads: “Vladimir Umanets, A Potential Piece of Yellowism.”
The newspaper speculated that it is a reference to the website www.thisisyellowism.com, a blog on conceptual art.
Reuters said that the incident took place around 3:30 pm London time.
The gallery was then closed for a short time while police investigated.
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"Tate can confirm that ... there was an incident at Tate Modern in which a visitor defaced one of Rothko's Seagram murals by applying a small area of black paint with a brush to the painting," said museum officials in a statement, according to the Guardian.
Wright said he saw the man looking at the painting just before the incident, the newspaper said.
"Then we heard the sound of a pen, but by the time we turned around he was pretty much finished with his tag. The pen ink then just dripped down the painting. Once we realised what had happened, we went to find a member of staff. They were really shocked when they came and saw what he had done."
Black on Maroon is part of a series that the Russian-American painter did for the Four Seasons restaurant in New York in 1958.
Scotland Yard said it was investigating the events, yet arrests have not been made.