An underground fire has left part of downtown St. Louis without power as temperatures soar.

The St. Louis Post-Dispatch reports that the fire that started Wednesday night has been extinguished. Ameren spokeswoman Trina Muniz says hot temperatures, combined with aging equipment, apparently led to cable failure and a fire in a manhole.

The outage is affecting more than 2,100 Ameren customers, and many more people. That's because sometimes, an entire high rise or apartment complex could be counted as one customer.

Several buildings, including St. Louis City Hall and the Carnahan courts building, are closed.

The outage comes as forecasters are predicting a heat index in excess of 100 degrees for the fifth day in a row.

Ameren says it hopes to restore power by midday Thursday.

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