Amazon has shut down construction of a new US warehouse after seven nooses were found on-site in the last month.
Construction has been stopped at the Windsor, Connecticut site until security measures have been put in place.
Amazon said it was “deeply disturbed by the incidents happening”.
It has offered a $100,000 (£70,589) reward for information on the nooses, the first of which was discovered on 27 April.
The looped rope is synonymous with the extrajudicial hangings, or lynchings, of mainly black people in the United States in the late 19th and early 20th Centuries.
Amazon spokeswoman Kelly Nantel said: “We continue to be deeply disturbed by the incidents happening at the construction site in Windsor and have ordered it’s shut down until necessary security measures can be put in place.
“Hate, racism or discrimination have no place in our society and are certainly not tolerated by Amazon – whether at a site under construction like this one, or at one that we operate.”
She added the firm was working with the town and Windsor Police Department on the matter.
Windsor Police said in a statement that the first noose was found hanging from a steel beam within the building on 27 April, before five more ropes “that could be interpreted as nooses” were found on several different floors two days later.
Construction continued until a seventh was found on Wednesday.
The ropes were hung in areas without surveillance. Hundreds of construction workers employed by a number of different companies were working on the site, which meant the police have limited information, the statement said.
Amazon has increased the reward on offer from $50,000 to $100,000 in recent days.
However, in a press conference, president of the Connecticut chapter for the National Association for the Advancement of Colored People (NAACP), Scot X Esdaile, said, he had been disappointed by the response so far.
“We’ve been striving to get on the site, to talk to individuals to make sure that they were safe. And still, we have not gotten onto the site yet,” he said.
“It’s imperative … that we make sure that those individuals are safe and that they’re out of harm’s way.”
The Connecticut state police and agents from the Federal Bureau of Investigation (FBI) are assisting local police with the investigation.
“The implications of a hanging noose anywhere are unacceptable and will always generate the appropriate investigative response,” FBI special agent David Sunderberg said in a statement to local news outlet WTNH.