A piece of mail containing a harmless white powder the sender purported to be anthrax spores was sent to the couple on Feb. 12, according to the daily newspaper.
The package was addressed to both Markle and Prince Harry, who are scheduled to tie the knot on May 19.
Royal staff following the usual security precautions discovered and seized the mail before the couple could handle it.
“The substance was tested and confirmed as non suspicious,” a spokesperson for London’s Metropolitan Police told HuffPost.“Officers are also investigating an allegation of malicious communications which relates to the same package.”
The Standard reported the package was delivered to Kensington Palace. The police said it was sent to St. James’s Palace.
No arrests have been made. A Kensington Palace spokeswoman told HuffPost it would not comment.
A similar non-toxic package was sent to British Home Secretary Amber Rudd’s parliamentary office. Authorities are probing whether there is a link.
Anthrax is a “serious infectious disease,” according to the Centers for Disease Control and Prevention, and can cause “severe illness in both humans and animals” who come into contact with it. It can be treated with antibiotics.