The Third Street Tunnel in downtown Washington has fully reopened after a water main break caused it to close for a week.

       Officials said Sunday night the tunnel had reopened for Monday morning’s rush hour traffic. Part of the tunnel reopened late last week, but the southbound lanes weren’t fixed until Sunday night.

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       The tunnel was closed last Monday because of a break in an eight-inch water main behind an auxiliary wall. The break flooded the road and left hundreds of nearby residents without water for hours that day.

       The tunnel, which runs beneath the National Mall, is a key commuter route into downtown Washington. Fixing the break was challenging because it was in the tunnel and there were multiple utilities and infrastructure issues to deal with, according to D.C. Water officials.

       Part of 3rd Street Tunnel in D.C. reopens after water-main break, but repair work is expected to take days

       Crews “spent several days assessing damage, backfilling voids caused by the force of the water, and performing concrete and pavement repairs,” D.C. Water officials said in a statement.

       David L. Gadis, D.C. Water’s chief executive and general manager, said in a statement, “We thank you for your patience.”

       He said his agency and the city’s Department of Transportation and others had worked together to fix the tunnel and roadway.