New Britain city hall was evacuated on Friday because of a suspicious envelope delivered to the building.
Mayor Timothy O'Brien said the envelope was delivered to his office, but did not say if the mail was addressed to him. It was opened by a member of his staff, O'Brien said.
City Hall will be closed until Monday, according to officials. A hallway connecting city hall to the Board of Education building is also closed.
According to federal law enforcement sources, the suspicious letter appeared to be similar to letters sent to schools in Enfield, Madison and Newington earlier this week.
Approximately 40 suspicious letters have turned up at schools and other places nationwide in the past two weeks. They all have been mailed from Texas, and almost all contained an anti-law enforcement message, the source said.
The letters sent to the three schools in Connecticut contained a white powder, but authorities would not say if the letter sent to New Britain City Hall contained any powder.
No one was injured in any of the incidents.
