QUINCY — Two more fires struck south of Boston on Tuesday, including one that was deliberately set, in circumstances that were similar to a dozen other recent blazes in the ­region that authorities have labeled as suspicious or arson.

Each fire on Tuesday, in Quincy and Hanson, claimed a vacant building and began in the early morning hours, as was the case in many of the fires in eight other communities south of Boston dating back to September. In Quincy, authorities determined the fire that destroyed an empty two-story house that had been used as a commercial building was deliberately set.