Federal authorities have been stepping up their efforts to locate a “person of interest,” who calls himself “The Bishop,” since he mailed incomplete explosive devices to financial services companies in the United States several weeks ago. A forensic investigation has been under way since early February, and offers of a reward (up to $100,000) for information leading to The Bishop’s arrest and conviction were followed recently by the release a sketch, showing what federal authorities believe “The Bishop” might look like...