The post office, the middle school and the town hall in Thomaston were evacuated on Tuesday morning after someone sent a letter, making a bomb threat, to the post office at 150 Main St.
The letter said there was a bomb in the building, officials said, which prompted evacuations of the three buildings, which are all near each other.
Police said they have identified a suspect but had not made an arrest as of 1:30 p.m.
No bomb was found.
