The FBI is investigating anti-Semitic vandalism at a Jewish summer camp in Michigan.

At least two people spray-painted a swastika on a sign outside Camp Agudah Midwest, an Orthodox overnight camp in South Haven, on Saturday night or Sunday morning, The Associated Press reported. The vandalism coincided with the holiday of Tisha b’Av, when Jews mourn the destruction of the ancient Temples.

Vandals also damaged a building at the camp and spray-painted swastikas on a nearby picnic table and car.

In the aftermath of the incident, the camp said it has hired a night security guard and stepped up security.

According to its Facebook page, the camp is affiliated with the haredi Orthodox Agudath Israel of America and runs a series of separate four week sessions for girls completing the grades 4-10 and for boys completing the grades 4-12.

The incident follows a similar attack at Camp Karlin Stolin, a Jewish summer camp in Highland, New York, this summer. According to reports, three 18-year-old assailants threw bottles and coins at campers and staff. Two of the perpetrators are being charged with a bias crime for aggravated harassment and conspiracy. The third suspect is facing a conspiracy charge.