Fairfield police say an aggressive pit bull has forced postal carriers to stop delivering mail along parts of Fairview Avenue. They say the delays date back to April 25, when the dog broke through an invisible fence at its Fairfield Avenue home and bit a postal worker. A post office spokesperson says mail service has been suspended at the house and that the town's dog warden is now accompanying the mail carrier on his route. The dog's owner says he is working with local authorities, who are urging him to secure the dog when it's outside.