Additionally, the New York City Fire Department confirmed the same details, notably, that the substance was not poisonous or corrosive.
The contents of a letter that saw US President Donald Trump's daughter-in-law hospitalised have been revealed.
The letter wrote, "you are an very bad person".
The letter was reportedly addressed to Trump Jr. and was mailed to the apartment unit belonging to Vanessa, where she opened it and found the unknown substance. You are getting what you deserve.
Firefighters decontaminated her and two others at the scene, and she was taken to a hospital afterward.
Authorities are still looking into who sent the letter, which contained a white powder that appeared to be corn starch.
"You are an very bad person", the letter posted to the United States president's eldest son purportedly read, according to officials quoted in NBC New York.
Trump Jr., along with his brother, Eric, took over managing the Trump Organization after their father won the presidency.
Vanessa Trump, opened the letter and discovered the powdery substance and note, sources said.
On Tuesday, the couple was seen for the first time since the white powder scare. "This risky and reckless act goes beyond political differences".
Trump Jr. tweeted later Monday that his wife and children were "safe and unharmed" after the incident. "Truly disgusting that certain individuals choose to express their opposing views with such disturbing behaviour".
"Thinking of [Vanessa Trump] & wishing I was by her side today", Ivanka Trump wrote.