HARTFORD — A New Haven man who has sent threatening letters in the past is in custody after suspicious packages were found at four downtown Hartford buildings, including a government office and a courthouse.

U.S. Attorney for Connecticut John Durham said Wednesday that 51-year-old Gary Joseph Gravelle was charged with violating the terms of his release from federal prison in 2015.

Prosecutors said Gravelle is being investigated in connection with threats and letters containing white powder sent to several government offices and organizations.

Authorities on Wednesday closed down streets and partly evacuated at least one building following reports of at least five suspicious packages. The structures included a state government building, two office buildings and the federal courthouse.

No injuries were reported and at least two packages appeared to contain baby powder.