President Donald Trump’s daughter-in-law was taken to a Manhattan hospital as a precaution on Monday after a suspicious letter containing an unidentified substance was sent to her apartment, senior law enforcement and city officials told NBC News.

The letter was addressed to Vanessa Trump’s husband, Donald Trump Jr., the eldest child of the president and his ex-wife Ivana.

Police investigating suspicious envelope addressed to Trump Jr.

After the letter was opened, three people at the residence were taken to New York Presbyterian-Weill Cornell Medical Center strictly as a precaution, the New York City Fire Department said.

There is no indication anyone suffered any injuries and no sign that the substance was a hazardous material or a biological agent.