Police and fire department officers stand outside Trump Tower where detectives and other agencies were investigating a suspicious white powder found inside the building, Thursday, April 28, 2016, in New York. Six people were being evaluated by emergency medical crews after an envelope containing a white powdery substance was mailed to Republican presidential candidate Donald Trump's campaign office in New York City. Police said a Trump staffer opened the letter containing the powder and immediately called police. It was unclear if the envelope also contained a letter. (AP Photo/Kathy Willens)
The Associated Press
NEW YORK (AP) - An envelope containing a suspicious white powdery substance caused a scare when it was opened at a campaign office of Republican presidential candidate Donald Trump, but it later was deemed to be harmless.
The envelope was mailed to Manhattan's Trump Tower, near Central Park, police said. A campaign staffer opened the envelope Thursday night and immediately called police.
Five Trump staff members working in the office and a police officer who responded were temporarily isolated and evaluated. The substance was tested, and a few hours later authorities said it wasn't hazardous but it would need to be tested some more for them to determine what it is.
Trump campaign spokeswoman Hope Hicks referred questions about the brief scare to the U.S. Secret Service, which didn't immediately respond to a message seeking comment.
Powders sent through the mail have been cause for concern since at least 2001, when anthrax-tainted letters were sent to media outlets and offices, killing five people.
In March, an envelope that contained a non-hazardous white powder and a threatening letter was mailed to the apartment of Trump's son Eric Trump, who has campaigned for him. The handwritten note, postmarked from Boston, said: "If your father does not drop out of the race, the next envelope won't be a fake."
Two days later, a threatening letter was sent to Trump's sister Maryanne Trump Barry, a judge who sits on the U.S. Circuit Court of Appeals for the 3rd Circuit in Pennsylvania. The FBI said at the time it was working alongside the Secret Service and the Marshals Service to investigate.
Trump, the front-runner for the Republican presidential nomination, has been criticized by some political rivals and voters for his comments on topics including women, refugees and immigrants, such as when he said some Mexican immigrants in the U.S. illegally are "rapists."
New York Police Department Counterterrorism officers stand outside Trump Tower Thursday, April 28, 2016, in New York, where police were investigating a suspicious white powder found earlier in the day. Six people were being evaluated by emergency medical crews after an envelope containing a white powdery substance was mailed to Republican presidential candidate Donald Trump's campaign office in New York City. Police said a Trump staffer opened the letter containing the powder and immediately called police. It was unclear if the envelope also contained a letter. (AP Photo/Kathy Willens)
The Associated Press
New York Police Department Counterterrorism officers join other officials outside Trump Tower, Thursday, April 28, 2016, in New York, where police were investigating a suspicious white powder found earlier in the day. Six people were being evaluated by emergency medical crews after an envelope containing a white powdery substance was mailed to Republican presidential candidate Donald Trump's campaign office in New York City. Police said a Trump staffer opened the letter containing the powder and immediately called police. It was unclear if the envelope also contained a letter. (AP Photo/Kathy Willens)
The Associated Press
Employees stand inside the lobby of Trump Tower where police were investigating a suspicious white powder found Thursday, April 28, 2016, in New York. Six people were being evaluated by emergency medical crews after an envelope containing a white powdery substance was mailed to Republican presidential candidate Donald Trump's campaign office in New York City. Police said a Trump staffer opened the letter containing the powder and immediately called police. It was unclear if the envelope also contained a letter. (AP Photo/Kathy Willens)
The Associated Press
Police officers stand outside Trump Tower on Manhattan's Fifth Avenue where detectives and other agencies were investigating a suspicious white powdery substance found inside the building, Thursday, April 28, 2016, in New York. An envelope containing the white powdery substance caused a scare when it was opened at a campaign office of Republican presidential candidate Donald Trump, but it later was deemed to be harmless. (AP Photo/Kathy Willens)
The Associated Press
A doorman holds the door for investigators from the Department of Environmental Protection and other agencies who were investigating the presence of a suspicious white powdery substance found at Trump Tower on Manhattan's Fifth Avenue, Thursday, April 28, 2016, in New York. An envelope containing the white powdery substance caused a scare when it was opened at a campaign office of Republican presidential candidate Donald Trump, but it later was deemed to be harmless. (AP Photo/Kathy Willens)
The Associated Press