Authorities are investigating after they say a suspicious powder was found at Trump Tower.

Officials say the call came in shortly after 8 p.m. Thursday.

Police say the suspicious powder was found in a letter addressed to Donald Trump's campaign office in Midtown, but they wouldn't say where specifically the powder was found in the building.

Police say the building was deemed safe at around 10:45 p.m. Thursday.

According to the NYPD, six people encountered the substance, and three people were evaluated at the location.

Investigators say the substance is not hazardous and is being evaluated by the Health Department.

They have not indicated what the powder is yet.

Trump was not in the building at the time.

Back in March, an envelope with a non-hazardous white powder and threatening letter was sent to the apartment of Trump's son Eric.