Many of the numbers seem to be tied to TextNow, a text messaging service that allows users to obtain untraceable, “burner” phone numbers, according to NBC News. TextNow said in a statement to the news network that it was aware of the racist campaign and was trying to prevent its service from being used to harass people.

Racist texts with references to ‘picking cotton,’ ‘plantations’ and ‘slave catchers’ have been sent to Black people in at least 20 U.S. states shortly after the presidential election. The Trump campaign denies any involvement.