The suspicious white powder that was found inside an envelope opened at the New York campaign office of US Republican presidential candidate Donald Trump has been found to be harmless.
The envelope was mailed to Trump Tower in Manhattan and opened by a campaign staff member on Thursday night (local time), New York police say.
Five employees who were working in the office and the police officer who responded were temporarily isolated and evaluated.
The substance was tested, and found to be non-hazardous but further testing will be required to work out exactly what it is.
Trump campaign spokeswoman Hope Hicks has referred questions about the scare to the US Secret Service, which didn't immediately respond to requests for comment.
Powders sent through the mail have been a 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 US 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 criticised 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 US illegally are "rapists."