Officials say vandals have spray painted apparent references to a Peru prison massacre on a wall at the National World War I Museum in Kansas City.

KMBC-TV reports that the museum’s “Dedication Wall” was defaced with red spray paint that said, “Glory to the fallen martyrs of El Frontòn, Callao, Lurigallcho.” The text apparently is in relation to the 33rd anniversary of prison massacres in Peru that resulted in more than 200 deaths.

Museum spokesman Mike Vietti says police have opened an investigation into the matter. He says Stephen Haith, owner of DSG Equipment and Supplies, has offered to clean the stone portion of the wall at no cost.