On Aug. 18, a collapse in wastewater infrastructure spilled an estimated 2 million gallons of untreated sewage into the Flint River, city officials report.

The spill comes just months after inspectors warned the city that its wastewater infrastructure was inadequate, according to MLive.

On Aug. 20, two days after the spill, the city filed a partial report with the state Department of Environment, Great Lakes and Energy citing the cause of the spill as a “flash flood event” which caused settling tanks to overflow. The city did not initially reveal the magnitude of the spill.

Although the Flint City Council recently approved nearly $1 million toward sewage facility upgrades, the changes had not yet been implemented, the Root reports.

City officials cautioned residents to avoid coming into contact with the water in the river due to bacteria. The local government has not yet announced plans for resolving the spill.