Letters sent in recent days to the White House and to local law enforcement agencies in Texas contained the lethal substance ricin, and investigators are trying to determine whether other envelopes with the toxin were sent through the postal system, a law enforcement official briefed on the matter said on Saturday.
Investigators believe that the letters were sent from Canada and have identified a woman as a suspect, the official said.
The letter to the White House, which was addressed to President Trump, was intercepted, as were the letters to a detention facility and a sheriff’s office in Texas.
The envelope to the White House was caught at the final off-site processing facility where mail is screened before being sent to the White House mail room, according to a second law enforcement official. The Postal Service irradiates mail that is addressed to the White House and other federal agencies in the Washington area, and the mail is sorted in a facility that samples the air for suspicious substances.