April 21 (Reuters) - The Limetree Bay refinery in St. Croix, U.S. Virgin Islands, has resumed producing fuel following an entire plant shutdown earlier this month, two sources familiar with the matter said on Wednesday. Shipping data reviewed by Reuters indicates that the refinery is producing vacuum gas oil and ultra-low-sulfur diesel. The plant halted operations earlier this month due to an undisclosed operational issue. (Reporting by Laura Sanicola; Editing by Leslie Adler)