Leipzig now have 62 points with three games left although Dortmund, still hopeful of chasing down Bayern Munich for the title, have a game in hand.
They face Fortuna Duesseldorf on Saturday.
Leipzig remain comfortably on course for a return to the Champions League, having already made the quarter-finals this season, with a six-point cushion over closest pursuers Borussia Moenchengladbach and Bayer Leverkusen who play at the weekend.
Spanish midfielder Olmo found the net after nine and 11 minutes while substitute Christopher Nkunku was close to a third in stoppage time when a shot came off the post.
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