“The entire city of Houston is on a boil water notice. I’m reading that the people of Houston have not been notified by their local government. THEY’RE LITERALLY LEARNING THIS ON TWITTER,” wrote a Twitter user on Monday.

A boil water notice means consumers must boil their tap water before they drink it, use it to brush their teeth, make ice cubes, prepare food, clean feeding equipment or give it to their pets, according to water consumer body CCW.

“The city of Houston has everyone’s email address that has a water bill. We all pay it online. It’s beyond Unacceptable that we don’t have an email from them saying there’s a boil notice,” wrote another Twitter user.

According to the Texas Commission on Environmental Quality, a power outage at the East Water Purification Plant in Houston at 10:30 a.m. on Sunday led the water pressure to drop below the city’s required minimum levels for safety.

Six hours after the initial outage, the city issued the boil water notice to the 2.2 million customers of Houston Public Works.

Many are now complaining about the delayed response from city authorities, saying they had been drinking water for hours before finding out about the boil notice.

“How and why in the hell did Houston officials wait until around 8 p.m. to tell citizens that there was a power outage at a water plant in the morning,” tweeted journalist Jose de Jesus Ortiz.

“The City of Houston waited til damn near 10 pm to tell us we been on a boil water notice.. I been cooking and cleaning all day.. I done already poisoned myself,” wrote another Twitter user. Others complained about learning of the notice while they were drinking water.

The public is now being advised to boil all water used for food, drinking and brushing teeth for at least two to three minutes, and to avoid using chilled water lines from fridges. Ice from automated ice machines should also be avoided. Those who cannot boil water are advised to use bottled water instead.

But Houston Water Director Yvonne Williams Forrest said that the boil water notice was issued out of caution and to comply with regulatory standards rather than due to a real risk of contamination.

In an interview with KHOU 11, Forrest added that the system never lost pressure fully, “so there was never an opportunity for anything to enter our system. They just fell below the regulatory requirements.”

Texas Governor Greg Abbott directed the Texas Division of Emergency Management (TDEM) and the Texas Commission on Environmental Quality (TCEQ) to respond to the problems in Houston. He said the state is “immediately responding and deploying support to Houston as they work to get a safe supply of water back online.

“We have been in contact with Mayor Turner to offer the full support of the state, and we’re currently working to fulfil the city’s request for help with rapid turnaround of water sample results. I thank TDEM and TCEQ for swiftly responding to help address this issue,” Abbott added.

“We urge those that the boil water notice affects to continue heeding the guidance of local officials and take adequate precautions when boiling and using water. Together, we will ensure our fellow Texans are supported while the city’s water supply returns.”

The boil water notice is expected to be lifted on Tuesday morning, pending reviews of the city’s water samples from the TCEQ.