Sen. John Cornyn received a suspicious piece of mail on Wednesday, prompting an investigation from the Dallas Fire-Rescue hazardous material team. According to the Associated Press, all tests conducted on the mail were negative.
Calls to Cornyn's local and Washington D.C. offices have not been returned. NBC DFW says that an official with the senator's office confirmed the investigation.
Earlier today, the FBI issued a statement on two letters sent to government officials that tested positive for the poison ricin.
One letter, which was addressed to President Barack Obama, "was immediately quarantined by U.S. Secret Service personnel, and a coordinated investigation with the FBI was initiated." The other letter was addressed to Sen. Roger Wicker (R-Mass). Both pieces of mail were intercepted during routine mail screening.
The FBI noted that the test conducted "can produce inconsistent results." A more robust analysis of the granular substance will be released in the next 24 to 48 hours.
Reports of other suspicious pieces of mail have surfaced in Arizona and Michigan.
These incidents come on the heels of Monday's Boston Marathon bombing, which left at least three people dead and more than 150 wounded.
"There is no indication of a connection to the attack in Boston," the FBI said in a statement.