It may be related to your a/c system if the air handler or furnace is located in the attic. These systems have to drain the condensation they collect. They usually drain out through a pvc pipe some where near the condenser, this is called the primary drain line. If this line gets backed up, most installers include a secondary drain line that is usually run out through the eave. The secondary drain is usually connected to a large metal safety pan. I recommend having someone take a look in your attic ASAP to determine the real cause.