The U.S.-Canadian task force investigating the worst blackout in U.S. history has narrowed its probe to several causes, from a breakdown in power grid technology to poor control-room communication, investigators and energy experts say. Under political pressure to act quickly, investigators are expected late this month to release an interim report of their early findings, according to task force members. A final report at the end of the year or in early 2004 will detail causes of the cascading blackout that snuffed electricity Aug. 14, disrupting tens of millions of lives in eight states and Ontario. The report also will recommend steps to thwart outages. For the most part, the task force has worked in secrecy. Investigators signed confidentiality agreements, and the Energy Department has declined to comment. But in recent interviews, several task force members said more than a dozen possible blackout causes have been analyzed so far. Full Story