The break occurred at about 5 a.m. Initially, Chicago Street is closed between State Street (Illinois Route 31) and Crystal Street.
By 11 a.m. northbound State Street was back open, with southbound State Street expected to reopen by noon. Cleanup is expected to continue for the rest of the business day, a city official said.
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Chopper 7HD flew above the scene as muddy-looking water gushed from the break and covered the streets nearby in around a foot of water.
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Emergency crews were on the scene working to cap the break.