The Council on American-Islamic Relations (CAIR) headquarters in Washington, D.C., was evacuated Thursday after a foreign substance was received in the mail, a spokesman told TIME.
About three employees were quarantined inside the office after “white powder came out” of a "hate letter" about 1 p.m., CAIR spokesman Ibrahim Hooper said. They were released from quarantine around 3 p.m., according to Hooper. About 20 other employees were evacuated from the office.
“We get threats all the time," he said. "We get them on a daily basis. Clearly in the last few weeks since the Paris attacks, we have kind of gotten more.”
D.C.'s Metropolitan Police confirmed that they were investigating the incident. Hooper said preliminary tests show the piece of mail was not dangerous.
“The letter is now in the hands of the FBI," Hooper said.
CAIR is one of America's largest Muslim civil liberties organization. The group is headquartered on Capitol Hill and has regional offices across the country.
Hooper said the organization has received suspicious packages in the past.
“Several years ago, we received something similar," he said. "Every once in a while, some people send things with fecal matter.”