A hole several feet wide and several feet deep opened Thursday night in the pavement of 20th Street just east of Oak Street downtown.
Cracks in the pavement surrounding the hole suggested it could get bigger.
Orange cones were placed around the hole, and a worker for the city Water Services Department was guarding it Thursday night to make sure no one drove over and into it. The city planned to cover the hole temporarily with metal plates.
The cause of the hole was not immediately known.