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At a Glance Plymouth Rock symbolizes the spot where the Pilgrims landed in 1620.

The vandals also targeted other statues around Plymouth, Massachusetts.

Celebrations of the 400th anniversary of the Mayflower's landing begin in April.

Vandals have attacked a monument to one of the key moments in American history.

Over the weekend, they spray-painted Plymouth Rock, the stone that symbolizes the spot where the Pilgrims landed in 1620.

The vandals also targeted the Pilgrim Maiden statue, the National Monument To The Forefathers and four scalloped-shaped signs celebrating the upcoming 400th anniversary of the Mayflower landing, WBZ reported.

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Peter Sullivan, a resident of Plymouth, Massachusetts, discovered the graffiti on Plymouth Rock while walking around Pilgrim Memorial State Park.

"They vandalized everything. All the statues, monuments. These people went around town all night and did all kinds of damage ," Sullivan told CNN.

Plymouth Rock is managed by the Massachusetts Department of Conservation and Recreation as part of Pilgrim Memorial State Park . The opening ceremony for the Plymouth 400 celebration is scheduled for late April.

"We are saddened and sickened by the recent vandalism in our historic town," Plymouth Town Manager Melissa Arrighi tweeted. "We will begin clean up as soon as possible and the police are investigating."

No arrests have been made. Workers had removed the red spray paint, which included the letters MOF and the numbers 508, from the rock before noon, The Associated Press reported.