White powder was found on Wednesday in an envelope addressed to the New York judge who ordered Donald Trump to pay a USD 454 million civil fraud judgment.
It's the latest security scare involving people in key roles in the former president's legal cases.
A court officer screening mail at Judge Arthur Engoron's Manhattan courthouse opened the envelope around 9:30 a.m. Some of the powder fell out of the envelope and landed on the officer's pants, police said.
Preliminary tests were negative for hazardous substances, court spokesperson Al Baker said.
The courthouse operations office where the mail was opened was briefly closed, but the courthouse remained open. The officer and other workers who may have been exposed to the powder were temporarily isolated, Baker said. No injuries were reported.
Engoron had no exposure to the letter or the powdery substance, Baker said.
Wednesday's scare came less than two weeks after Engoron issued his verdict penalising Trump, his company and executives, including his two sons Eric and Donald Trump Jr., for scheming to dupe banks, insurers and others by inflating his wealth on financial statements used to secure loans and make deals.
Along with staggering financial penalties, the judge's ruling forced a shakeup at the top of Trump's company, putting the Trump Organisation under court supervision and imposing strict restrictions on how it does business.
In January, hours before closing arguments in the case, authorities had responded to a bomb threat at Engoron's Long Island home. Engoron's chambers have reported hundreds of harassing and threatening calls, emails, letters and packages.
Separately, on Christmas Day, Justice Department Special Counsel Jack Smith was the subject of a fake emergency call that reported a shooting at his home.
Smith, who is leading Trump's federal prosecutions in Washington, D.C., and Florida, has been the subject of numerous threats and intimidating messages since he was appointed and Trump began posting messages about him, prosecutors have said.
US District Judge Tanya Chutkan, who is overseeing Trump's Washington D.C. case, was targeted with a similar fake emergency call a few days later. Trump is charged in Washington with scheming to overturn his 2020 election loss and in Florida with hoarding classified documents after he left the White House.
On Monday, police in hazmat suits responded to Donald Trump Jr.'s Florida home after the former president's eldest son opened a letter that contained an unidentified white powder and a death threat. White powder was also found in a letter to Trump Jr. in 2018 and in mail sent to Eric Trump and Trump Tower in 2016.
Hoax attacks using white powder play on fears that date to 2001, when letters containing deadly anthrax were mailed to news organisations and the offices of two US senators. Those letters killed five people.