A cake attack has been perpetrated on the most famous painting in the world – but thanks to bulletproof glass, the “Mona Lisa” in the Louvre in Paris has not lost her legendary smile.

The 36-year-old perpetrator was admitted to a psychiatric ward, the police prefecture in the French capital announced on Monday. An investigation was launched against him. Pictures of the cream-smeared “Mona Lisa” caused a stir in online networks.

The Paris public prosecutor said the 36-year-old cake thrower was being investigated for “attempting to damage a cultural asset”. According to the police prefecture, after the act on Sunday, the man was taken to a psychiatric ward. The museum management told the AFP news agency on Monday that they did not want to comment on the incident.

Reports of a disguised man attacking a cake had previously caused a stir in online networks. A Twitter user named Lukeee wrote that while touring the Mona Lisa on Sunday afternoon, a man wearing a woman’s wig and cap got out of a wheelchair.

The attacker was disguised as an “old woman”, the Twitter user described. First he tried to smash the glass case in which the “Mona Lisa” is located. After that he “smeared cake on the glass and threw roses everywhere before he was grabbed by the security guards”.

Photos posted to Twitter and Instagram showed a man – apparently a warden at the Louvre – removing the cream from the painting’s protective pane. A photo or video of the actual cake throw did not initially appear on the Internet.

In a video shared by Twitter user Lukeee, a young man dressed in white can be seen standing next to his wheelchair and being escorted away by museum security personnel. Apparently he wanted his sensational action to be understood as a call for environmental protection.

“There are people who are destroying the earth,” he said in French in the video. “All artists, think of the earth. That’s why I made this. Think of the planet.”

In December 1956, a Bolivian threw a stone at the “Mona Lisa”, damaging the painting at the level of the Mona Lisa’s left elbow. As a consequence, the more than 500-year-old picture was protected with safety glass.

In 2005, the protective measures for the “Mona Lisa” were increased again. Since then, the picture has been behind bulletproof glass in a transparent box that ensures ideal temperature and humidity. In 2009, a Russian woman threw an empty teacup on the glass case, slightly scratching it.