WASHINGTON (AP) — Several federal and state agencies are investigating how racist mass messages were sent to people of color across the country in the wake of this week’s presidential election.

Text messages invoking slavery were sent to black men, women and children, prompting investigations by FBI and other law enforcement departments.

Anonymously sent messages have been reported in several states, including new york, Alabama, California, Ohio, Pennsylvania, Maryland and Tennessee. The FBI said it had communicated with the Justice Department about the messages, and the Federal Communications Commission said it was investigating along with federal and state law enforcement.

“These messages are unacceptable,” FCC Chair Jessica Rosenworcel said in a statement. She said the agency takes “this type of targeting very seriously.”

Although the texts varied somewhat, all instructed recipients to “board a bus” that would transport them to a “plantation” to work as slaves, officials said. They said the messages were sent to school-aged children and students, causing significant distress.

Whoever sent the messages used a VPN to hide their origin, Louisiana Attorney General Liz Murrill said Thursday morning.

The Maryland Attorney General’s Office said it has received several reports of racist text messages sent to black residents, including children. In a news release late Thursday, officials said the messages appear to be part of a nationwide campaign targeting people of color following the election.

“These messages are horrific, unacceptable and will not be tolerated,” Attorney General Anthony Brown said in a statement. Officials asked recipients of the texts to report them to local law enforcement.

Brown said it was troubling that children were included in data sets typically collected on adults, such as campaign donors or magazine subscribers.

“It’s an intimidating and threatening use of technology” that likely violated multiple laws, Brown said. “And our goal is to make sure we uncover all the facts and then use all the tools and resources available to us to hold whoever is behind these text messages accountable.”

Phone service provider TextNow said “one or more of our accounts” were used to send racist text messages and it quickly disabled those accounts for violating its terms and conditions.

“As part of our investigation into these messages, we learned that they were sent via multiple US carriers and we are working with partners and law enforcement to investigate this attack,” it said in a statement Friday.

Major carriers AT&T and Verizon both said it was an industry-wide problem and referred the comments to an industry trade group on Friday.

The U.S. wireless industry has blocked thousands of texts and the numbers that sent them,” said Nick Ludlum, SVP and Chief Communications Officer of CTIA, a wireless communications trade association. “Through CTIA’s Secure Messaging Initiative, participants have identified the platforms that bad actors used to send these messages and are working with law enforcement on this matter.”

These racist text messages span the entire country, predominantly targeting black Americans and, more specifically, middle school-aged black children.

Nicole, a North Carolina mother who asked that her last name not be used because of her profession, said she was disturbed and concerned about the messages her high school daughter showed her Thursday night. The texts instructed her to prepare to return to the plantation. This was her daughter’s first real experience with this type of racism, Nicole said, and as a parent, she didn’t want to have to have these conversations with her children.

“It’s like a slap in the face and shows me that it’s still a problem that hasn’t changed at all,” she said.

Nicole said her daughter didn’t say much after the message, deleted the message and went to bed. As for Nicole, she said she needs to sit and process her feelings. She said the situation was so shocking it didn’t seem real to her and she felt sad for her daughter.

“He has many friends of different races. She is the one who doesn’t see color and doesn’t see difference. So, I love it for her, it really showed her that not everyone is like her,” Nicole said. “Racism is still a very big thing in our country right now.”

Nicole said parents need to be vigilant, especially with older children, and have tough conversations, even if you don’t want to or feel like you have to.

“Whatever way it makes your child feel, approach it with open arms and be very receptive to it and take it day by day.”