Nyarko scored in the game's first minute when he got past a defender and put a ball through the legs of Dynamo goalkeeper Tally Hall for a quick lead.
The Fire doubled its advantage in the 19th on Paladini's low shot and Alex added a goal in stoppage time for the Fire (13-8-5), who improved to 4-1-0 over their last five games, climbing over Houston into third place in the Eastern Conference.
Brian Ching scored in the 90th minute for the Dynamo (11-7-9), whose winless streak stretched to four games.
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