Vandals struck the neighborhood near the 1700 block of South Delaware Street and left their spray-painted marks on homes, including exterior walls, garage doors and a few fences, Sgt. Dave Norris said.
"It looks like it happened sometime in the late evening," Norris said, adding that calls came in just after midnight on Saturday.
"Our gang unit is looking into it," Norris said.
Graffiti is not a common occurrence in the neighborhood, which is not considered a high-crime area, Norris said.
Anyone who sees suspicious activity in the area is asked to call 911 or the Police Department's non-emergency number at (650) 522-7700.
Those wishing to remain anonymous can call the Secret Witness Line at (650) 522-7676, send an anonymous text to (650) 262-3473 or e-mail sanmateo@tipnow.org.
