Authorities investigate letters with 'suspicious substances' sent to congressional, election offices

WASHINGTON (AP) — Federal authorities are investigating letters with “suspicious substances” that have been mailed to congressional and election offices nationwide and are urging recipients to treat the mailings as “potentially hazardous.”The investigation by the FBI, U.S. Postal Inspection Service and U.S. Capitol Police was first disclosed in a message from the Senate Sergeant at Arms obtained Thursday by The Associated Press. The notice, sent to Senate offices, said that law enforcement officials were working to intercept any additional letters, but “it is possible that some letters may reach their destinations.”In Congress, the threat appeared limited to the Senate, though the House was monitoring the situation, according to a person familiar with the matter who was not authorized to discuss the investigation publicly.An FBI statement said the bureau and the Postal Inspection Service were "investigating a series of suspicious mailings sent to various addresses nationwide, including