Police and fire personnel are investigating a suspicious substance found at Trump Tower on Thursday evening, officials said.

An FDNY spokesman said fire and rescue services responded just after 8 p.m. to a report of white powder found at 725 Fifth Ave.

It was not immediately clear what the substance was, but the spokesman said five people and one NYPD officer are being evaluated after they were exposed to the powder.

Police and fire officials are still at the scene investigating.

It’s not the first time a property with ties to Republican presidential hopeful Donald Trump has been sent a mysterious substance. Trump’s son Eric Trump received a letter with a powder inside at his Trump Parc East residence in March.

That substance was determined to not be hazardous, according to media reports.