Residents of Corpus Christi, Tex., have been warned to avoid all contact with tap water after a corrosive industrial chemical leaked into the local water system, forcing schools to close and prompting emergency bottled water deliveries throughout the Gulf Coast city.

Officials sent out an alert late Wednesday night telling the city’s 320,000 residents not to drink, bathe or prepare food with tap water after an accident in Corpus Christi’s industrial district caused an asphalt emulsifier to seep into water supplies. By Thursday night, the warning had been lifted in at least three neighborhoods but remained in effect for the majority of the city, including its commercial and residential hubs.

More than 100,000 cases of bottled water were donated to the city and were available for pickup Thursday at drive-through centers, with a restriction of one case per vehicle, Corpus Christi officials said.

“Our goal is to get us out of this as soon as absolutely possible so that our residents, our businesses, our customers can go back to their way of life,” city spokeswoman Kim Womack said in a news conference Thursday, as reported by ABC News.

Earlier, images circulated on social media showing long lines of people at grocery stores pushing shopping carts filled with bottled water. Walmart and other retail outlets said they were out of stock, multiple schools canceled classes and events, and some restaurants posted signs on their doors saying they had closed because of the advisory.

According to city officials, a “back-flow incident” at an industrial complex caused an estimated three to 24 gallons of a petroleum-based chemical known as Indulin AA-86 to enter the water supply.

The city has not publicly identified the source of the contamination, but Energy giant Valero said Thursday that it came from “third party operations in the area of Valero’s asphalt terminal,” according to the Corpus Christi Caller-Times. Initial reports indicated that it had come from Valero’s oil refinery.

“We do not believe this issue is being caused by Valero’s Corpus Christi refineries. While the City continues to investigate this issue, we do not believe the City’s water has been impacted,” Valero said in a statement to the Caller-Times. “We believe this issue is isolated to a lateral industrial line. Valero is offering its resources to assist the City in isolating the issue and to help confirm this has not impacted the City’s water supply.”

Corpus Christi city councilor Carolyn Vaughn told the paper that Ergon Asphalt and Emulsions Inc. may be responsible for the contamination.

A Corpus Christi law firm has obtained a temporary restraining order against Valero and Ergon barring them from destroying evidence related to the water contamination, the Caller-Times reported, and a second firm has filed a lawsuit against the companies alleging they “wantonly and recklessly” exposed city residents and businesses to toxic chemicals.

Representatives from Valero and Ergon did not immediately respond to requests for comment Thursday night. Valero told the Caller-Times that “while we have been named in lawsuits, we are not the source of the contamination in question,” and went on to blame Ergon. Ergon did not respond to requests for comment from the Caller-Times.

The state’s environmental regulator and the U.S. Environmental Protection Agency are investigating, according to the Caller-Times.

The exact ingredients in Indulin AA-86 are not publicly available, but the chemical is considered hazardous by the Occupational Safety and Health Administration. A safety sheet released by its manufacturer advises handlers to wear protective goggles and gloves when using it, saying it can cause skin and eye corrosion.

Officials said they became aware of the problem Wednesday afternoon, when they received a call from a refinery reporting an oily sheen in water from a faucet, according to the Caller-Times. Around 10:30 p.m., the city sent out a notice warning residents that “chemical substances may have contaminated our drinking water,” and saying only bottled water should be used until further notice. “Boiling, freezing, filtering, adding chlorine or other disinfectants, or letting the water stand will not make the water safe,” the notice said.

There have been no reports of illnesses or injuries so far, and tests Thursday showed no contamination outside Corpus Christi’s industrial district, the Caller-Times reported.

Some residents criticized the city for being slow to provide important details about the contamination and the response. A news conference Thursday afternoon was interrupted when a group of people began chanting, “What do we want? Clean water! When do we want it? Now,” the Associated Press reported.

“I feel there’s a lot more information that we’re not being told,” one resident, Reba Gandara, told the Caller-Times after the meeting. “We deserve transparency and [knowing] what’s going on with the water that is being provided to us. And it’s not just the water — it’s how it occurred.”

Another resident, Noe Garcia, said lines for bottled water have stretched out of stores and around the corner.

“It’s things like this that make us wonder, why do we have to pay taxes?” Garcia told ABC. “Why do we have to pay a water bill?”

Corpus Christi has experienced at least four water quality scares in the past 18 months. Between June and September 2015, the city issued two boil water advisories, one after E. coli contamination turned up in water samples and another after chlorine levels dropped in some areas. A third notice came in May 2016, when water in one area tested positive for bacteria, possibly indicating low disinfectant levels.

City councilor Rudy Garza Jr. said this week’s advisory raised questions about whether the city had taken the proper precautions to avoid contamination. He told the Caller-Times that the council would review the incident, along with the recent boil water advisories.

“The issue is that we’ve said that before,” he said, “and I’m sure people’s patience has grown very thin.”

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