The Ullrich water treatment plant in West Austin, which lost power Wednesday, is back online, but the citywide boil water notice remains in effect—and could linger.

Austin Water confirmed that its treatment plants are operating "in a stable mode" in a tweet Thursday morning. But the local utility added that it is "facing significant challenges to restore water distribution throughout the system" and is working to address the needs of critical customers, such as hospitals and power plants.

"The plant is back online," Austin Mayor Steve Adler told KXAN on Thursday morning, "and yes, we just need people to conserve at this point so we can just build up the reserves and the pressure, and the water boil will come off, but we need people to conserve water."

Water consumption surpassed typical usage by more than 250% on Wednesday, which Austin Water attributed to dripping faucets, leaking pipes and line breaks caused by freezing temperatures. This caused water pressure and storage to drop significantly, to below minimum standards, which can introduce contaminants into the water system.

As a result, Austin Water and city officials announced a citywide boil water notice late Wednesday. Residents are also being encouraged to conserve water and to stop dripping their faucets, despite the ongoing risk of burst pipes.

State law requires water testing before a boil water notice can be lifted. Toby Baker, executive director of the Texas Commission of Environmental Quality, said Wednesday that there are only 135 labs in the state that can do the necessary sampling, which means notices in Austin and elsewhere could linger, according to a report by the Texas Tribune; approximately 12 million Texans across 590 public water systems were experiencing disruptions in water service as of late Wednesday afternoon.