People across the country received racist text messages in the days after Donald Trump was elected to a second term for president, and now federal authorities are investigating.

“In multiple states, including Alabama, North Carolina, Virginia, and Pennsylvania, Black women, men, and students have reported receiving racist text messages from an unknown source, urging them to report to a plantation to pick cotton,” the NAACP said in a press release. Messages said variations of, “You have been selected to be a house slave,” or “You have been selected to pick cotton at the nearest plantation,” according to screenshots and news reports. They also often instruct recipients on where to go or when to be ready “With all of your belongings.”

CBS News reports that messages were sent from area codes in at least 25 states, but several were disconnected by Thursday. CBS found active accounts were linked to TextNow, which lets users create free phone numbers. TextNow told CBS it “learned that one or more of our accounts may have been used to send text messages in violation of our terms of service,” and shut them down.

Federal Communications Commission Chair Jessica Rosenworcel called the messages “unacceptable” in a statement and says the agency’s enforcement bureau was already investigating. “We take this type of targeting very seriously,” she says. The Federal Bureau of Investigation earlier said it was “in contact with the Justice Department and other federal authorities on the matter” and encouraged the public to report threats of violence to local law enforcement.