Federal and state authorities are investigating a wave of bigoted text messages sent anonymously that have spread alarm among Black Americans across the country this week, officials and recipients said.

The messages urged recipients in multiple states, including Alabama, North Carolina, Pennsylvania and Virginia, to report to a plantation to pick cotton, an offensive reference to past enslavement of Black people in the United States.

It is unclear who is behind the reported texts, how many people had received them, or how the recipients were targeted.