The Federal Bureau of Investigation (FBI) claims to work with police in Logan. However, the bureau refused to say whether they arrested the man who sent the letter or not.
"Because it is a pending problem, that's all we can say at the moment," said FBI spokesman Doug Davis, quoted by the Salt Lake City Tribune on Thursday (4/10/2018).
He asked the community to stay away from the location of the man's operation. However, the FBI assured the public that there was no wider threat.
As reported earlier, several letters sent to the Pentagon and the White House were tested positive for dangerous chemicals. The letter containing ricin poison was confiscated during the mail screening process.
Besides President Trump and Minister Mattis, there were other officials who were also sent suspicious letters. The officials included US Navy Chief of Operations Admiral John Richardson and Senator Ted Cruz. However, the letter was stated to be negative from ricin poison.
Pentagon spokesman Colonel Rob Manning told Fox News that the identity of the suspect was still unknown. But there are other reports that say former US Navy sailors are responsible for letters sent to the White House, Pentagon and Cruz offices.
"On Monday, the Pentagon Force Protection Agency detected suspicious substances during mail screening at the Pentagon's remote screening facility," Manning said.