NEW YORK (CBSNewYork) — President Donald Trump’s daughter-in-law was taken to the hospital Monday morning after opening a letter containing a suspicious substance.

It wasn’t the kind of thing that most would expect to happen at a quiet Sutton Place building — police and secret service agents arrived out of nowhere to stand guard.

“It’s awful, it’s atrocious,” Susan Grella told CBS2 Political Reporter Marcia Kramer.

The letter was addressed to Donald Trump Jr. and was sent to a Sutton Place home owned by him but occupied by his mother-in-law, who gave it to his wife Vanessa.

Vanessa opened the envelope and discovered the white powder inside, 1010 WINS Sonia Rincon reported.

She called 911 after opening the envelope. Police say she said she was coughing and felt nauseous.

Vanessa and two other people were taken to a hospital to be evaluated, law enforcement sources told WCBS 880. A police department spokesman says a preliminary test of the powder indicated it wasn’t dangerous.

Vanessa was not hospitalized but was being tested at the hospital out of an abundance of caution, CBS News’ Pat Milton reported.

Law enforcement sources told CBS2 the substance turned out to be corn starch.

The letter was postmarked in Boston, and a source told WCBS 880 a note inside with the powder was harassing, but not threatening.

A hazmat unit also responded to the scene.

Thankful that Vanessa & my children are safe and unharmed after the incredibly scary situation that occurred this morning. Truly disgusting that certain individuals choose to express their opposing views with such disturbing behavior. — Donald Trump Jr. (@DonaldJTrumpJr) February 12, 2018

“Thankful that Vanessa & my children are safe and unharmed after the incredibly scary situation that occurred this morning,” Trump Jr. wrote on Twitter. “Truly disgusting that certain individuals choose to express their opposing views with such disturbing behavior.”

“The Secret Service and our law enforcement partners in New York City are investigating a suspicious package addressed to one of our protectees received today in New York, New York. This is an active investigation and we cannot comment any further,” Secret Service Special Agent Jeffrey Adams said in a statement.

Thinking of @MrsVanessaTrump & wishing I was by her side today. No one deserves to be frightened this way. There is no excuse. — Ivanka Trump (@IvankaTrump) February 12, 2018

“I know that the president spoke with [Vanessa],” White House Press Secretary Sarah Sanders said. “Beyond that, at this point, it’s an ongoing and active investigation, so I can’t comment any further.”

“Thinking of @MrsVanessaTrump & wishing I was by her side today,” Ivanka Trump posted on Twitter. “No one deserves to be frightened this way. There is no excuse.”

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)