A 20-feet red and white banner reading "Refugees Welcome" was illegally placed on the base of the Statue of Liberty on Tuesday afternoon.
National park police officers were investigating how the banner got on, the NBC News reported.
The banner, measuring about three feet by 20 feet, was affixed by nylon rope to the wall of the public observation deck at the base of the statue, according to the National Park Service.
It was taken down by rangers later.
A social media account 'Alt Statue of Liberty', who claimed responsibility for the stunt, said: "We have no formal group -- just private citizens who felt like we needed to say something about the America we believe in."
Attaching banners to national monuments is prohibited.
(With inputs from IANS)