Community Health Center on Main Street in Old Saybrook was evacuated after an employee opened mail containing white powder Friday morning and the center is closed for the day.
Leslie Gianelli, a spokesperson for Community Health Center, Inc., said three employees were in the office and they were evaluated and cleared.
This was one of several white powder incidents in Connecticut. There were other incidents in Hartford, which turned out to be baby powder. There were also incidents reported in New Haven and Bristol.
There was a heavy police presence on Main Street in Old Saybrook Friday morning, employees were evacuated and members of the state police bomb squad responded.
A source close to the incident said a letter was taken to the state Public Health Laboratory.
No additional information is available and the FBI had no comment.
No arrests have been made in the case, but the U.S. Attorney's Office said 51-year-old Gary Gravelle, of New Haven, is being questioned.
He was arrested on a supervised release violation unrelated to these cases and is in custody.
Gravelle is known to federal authorities. In 2013, he was sentenced in Bridgeport federal court to 70 months in prison for mailing threatening letters and he was released from federal prison in November 2015.