A police department in upstate New York is alerting residents about a Ku Klux Klan advertising campaign that involves bags containing flyers and cat litter.

AP/Jason Turner - apimages.com

Klan members are apparently tossing the plastic bags on residents' lawns at night, and the Fulton County Sheriff's Department is soliciting the public's help in identifying the suspects. Officials suspect the cat litter is being used as a weight for the bags.

"Please be aware that there are individuals going around representing themselves as members of the KKK," the sheriff's office wrote in a Facebook post on Saturday. "Recent activity has them in Northville over night where they are leaving small bags containing informational pamphlets and kitty litter. This is NOT harmful and can be thrown out."

The KKK chapter's leafleting effort is a troubling reflection of a national trend.

Though the white supremacist hate group has seen its number of active chapters decline by 34 percent from 2016 to 2017, that comes after 134 percent spike the previous year, according to the Southern Poverty Law Center (SPLC). And it comes as active hate groups in general—especially those targeting Muslims—have experienced rapid growth.

SPLC - splcenter.org

The flyers found in Northville, New York, advertise for a KKK-organized July 8 rally that's being held in Charlottesville, Virginia. The rally is set to take place near a Confederate statue that has been the site of white nationalist protests in recent months. Other flyers advertising for the rally (sans cat litter) were found in Texas and Alabama over the weekend, Vice reported.

Last year, "the activities of Klan groups were largely limited to anonymous leafleting—an easy task, typically requiring only one person, that virtually guarantees media attention," the SPLC reported. The watchdog group "found that various Klan groups had distributed white supremacist fliers 117 times in 26 states last year."