FBI investigates letters with unknown substance sent to US election offices

Federal authorities are investigating a series of suspicious mailings sent to election offices across the US containing an unknown substance.

• The FBI and the Postal Inspection Service said they are investigating suspicious mailings sent nationwide, some of which contained an unknown substance.
• Envelopes containing a powdery substance led to evacuations at election offices in Louisiana and Oklahoma this week.
• The Senate sergeant at arms told members that law enforcement was working to intercept additional mail, urging recipients to treat it as "potentially hazardous."
• Postal Inspection Service official Brendan Donahue said "any threat or attack on an election official is unacceptable."
• At least five Senate Democrats' offices were among the targets of the suspicious letters, with most of the mail intercepted before delivery.