(JTA) — Unidentified individuals smashed two headstones at a Dutch Jewish cemetery.

The vandalism was discovered last week at the Jewish cemetery of Vlissingen in the south of the Netherlands. It is not immediately clear whether the incident was anti-Semitic, the news site jonet.nl reported on Dec. 25.

One of the smashed headstones covered the grave of Joseph van Raalte, a director of the Royal Schelde shipyard, which used to build vessels for the Dutch Navy. Police are looking for suspects but have none in custody.

Earlier in the week, the Jewish community of Heemstede near Haarlem inaugurated a new synagogue in a building which, according to the Heemsteedse Courant daily, displays few Jewish symbols on its facades for security reasons.

Anti-Semitic incidents increased dramatically in the Netherlands during Israel’s summer operation against Hamas in the Gaza Strip. The CIDI watchdog group registered 105 complaints during the two-month operation. By comparison, the organization registered 147 during the whole of 2013.

In one incident this summer, a firebomb was hurled at the Amsterdam home of a Jewish woman from Mexico who displayed an Israeli flag on her porch.

The incidents are causing a growing number of Dutch Jews to avoid displaying Jewish symbols, according to Manfred Gerstenfeld, a scholar of anti-Semitism in Europe who grew up in the Netherlands and has written more than 10 books on the subject of Jew-hatred in Europe.