Iowa authorities confirmed Friday that recorded phone calls citing the slaying of an Iowa college student are being used to promote white supremacist views, but they said there’s little they can do despite an outcry from Hispanics and other groups.

Prosecutors have no authority to step in because there’s no apparent effort to deceive anyone for commercial purposes, said Lynn Hicks, a spokesman for the Iowa attorney general’s office.

Hicks said Iowa law addressing robocalls, or autodialing, bars using the equipment for fraudulent purposes, “but there are all kinds of exceptions for noncommercial purposes and for nonprofit organizations.” He called it a “really tricky First Amendment issue.”

It’s unclear how many of the robocalls have been made since they began Tuesday, two days after Mollie Tibbetts’ funeral in Brooklyn, Iowa.

Authorities have said the University of Iowa student was abducted while she was out for an evening run in Brooklyn on July 18. The man charged in her death, 24-year-old Cristhian Bahena River, is also suspected of being in the U.S. illegally. President Donald Trump and other politicians quickly noted that element of the case and called for changes to immigration law.

The robocalls reference comments Tibbetts’ father made in defense of Hispanics when he addressed friends and family at her funeral. The calls question whether his daughter would feel the same if she were still alive and describe Rivera as “an invader from Mexico.” The calls also reference immigrants living the U.S. illegally when saying: “We don’t have to kill them all, but we do have to deport them all.”

The calls were first reported by an Iowa political website, Iowa Starting Line.

The recordings say the calls are being paid for by The Road to Power, an Idaho-based group with a website and neo-Nazi podcast linked by officials to an Idaho man who, according to local media, distributed racist CDs in a high school parking lot in Sandpoint, Idaho, in December. The man didn’t return a phone message Friday from The Associated Press.

The caller ID shows a Brooklyn area code and local prefix, but Ted Atkinson with the Brooklyn Mutual Telecommunications Cooperative said it’s unclear where the calls are coming from.

Shortly after the River led investigators to Tibbetts’ body in a cornfield in late August, Iowa Gov. Kim Reynolds said local residents were heartbroken.

“We are angry that a broken immigration system allowed a predator like this to live in our community, and we will do all we can to bring justice to Mollie’s killer,” she said at the time . But on Thursday Reynolds said: “It’s unconscionable that somebody would take and utilize a tragic death like Mollie Tibbetts. It’s just ridiculous, unconscionable and repulsive.”

Nearly 100 people held a prayer vigil Thursday in Des Moines to support the Tibbetts family and urge Hispanic unity in the face of the robocalls.