DURHAM, N.C. (AP) — Officials at a pharmaceutical plant in North Carolina have launched an investigation into the discovery of two nooses at a construction site.

The News & Observer of Raleigh reports Merck and local authorities are looking into the incidents.

Plant management notified employees of the first noose just over a week ago.

The second noose was reported to the Durham County Sheriff’s Office last week.

Merck’s Durham plant was one of two selected to help manufacture the Johnson & Johnson COVID-19 vaccine earlier this year.

Loops of rope have long been used to intimidate African-Americans because they evoke lynchings.