Federal investigators are trying to determine who is responsible for a "series of suspicious mailings" that were sent to election officials in several states.
In a statement to Scripps News, the U.S. Postal Inspection Service said some of the letters contained an unknown substance.
"We are also working with our partners to determine how many letters were sent, the individual or individuals responsible for the letters, and the motive behind the letters," Michael Martel, national public information officer for the agency, said.
On Tuesday, Connecticut Secretary of State Stephanie Thomas revealed that a "suspicious envelope" was intercepted at a postal facility in West Hartford.
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Thomas said the envelope was taken to a state lab for processing.
“For almost two years, we have been working as a team preparing for events such as this and we are now seeing why that work has been so important," Thomas said.
The suspicious letters come at a time of increased political tension in the country and follow an apparent assassination attempt on former President Donald Trump.
Republicans and Democrats are blaming each other for what they describe as dangerous rhetoric while also condemning political violence.
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