ROCK FALLS, Ill.  — Rock Falls crews are investigating why a control panel failed at the city pump station, leading to a sewer backup that forced officials to shut off water to the entire city.

Sauk Valley Media reports that the city knows only that power to the panel went out last Thursday, but not why.

Mayor Bill Wescott says it could take several days to pinpoint the cause.

The failure caused 190,000 gallons of sewage to back up, prompting the city shut off water for about 18 hours.

Get news headlines sent daily to your inbox

A precautionary boil-water order was put into effect after water was restored on Friday. The order was lifted on Sunday.

While the order was in effect, the city handed out bottled water to residents at four sites, where portable toilets also were set up.