The Winnipeg Police Service closed Mcphillips Street between Logan and Jarvis due to flooding on Tuesday.
Police tweeted the closure at 6:47 a.m.
The underpass later opened back up at 2:03 p.m.
The city says the flooding was caused by a power outage which caused the pumps to stop running.
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The reopening of the underpass took several hours as backup generators were set up to operate the pumps and it took some time for the water to drain fully.
flooding was also reported at the underpass on Annabella between Higgins and Sutherland and two cars appear to have been stuck in the water.
However, police say the water has since been cleared and the stalled vehicles have been removed.