Authorities in Washington said 24 people were quarantined Thursday before it was determined that a suspicious letter posed no threat.

Assistant District of Columbia Fire Chief Lawrence Schultz said the letter received by the Department of Veterans Affairs sparked police and fire crews to respond to the building after it was found to contain a written threat and a fair amount of powder, The Washington Post reported Thursday.

The 24 mail room workers were quarantined for about 90 minutes before authorities carried out tests on the powder and determined that it did not contain any biological weapons or other dangerous substances.

An entrance to the McPherson Square Metro station was shut down and traffic in the area was detoured before the letter was found not to pose a threat, authorities said. (c) UPI