A white powder was found in a stack of mail by a staffer in Meeks's office, according to the lawmaker's Chief of Staff Sophia Lafargue. The substance was found in a stack of envelopes, but its origin wasn't clear, Lafargue said.

Meeks's office immediately called the Capitol Police when the substance was found. 

Lafargue said the powder was found sometime around noon.

This incident follows multiple mailings of ricin, a deadly poison made from castor beans, to a number of elected officials, including Sen. Roger WickerRoger WickerA guide to the committees: Senate Pruitt confirmation sets stage for Trump EPA assault Price huddles with Senate GOP on ObamaCare MORE (R-Miss.) and President Obama.

Since the ricin-laced letters were discovered, the FBI has been investigating.

Over the weekend law enforcement charged James Everett Dutschke with sending the letters. Dutschke was arrested Saturday by federal marshals.