CORPUS CHRISTI, Texas — City officials confirmed Saturday that there are four cases of people who have skin and intestinal issues consistent with exposure to contaminated water.

The Caller-Times also has confirmed that the Texas Commission on Environmental Quality's initial report shows a backflow issue at a mixing tank Dec. 7. However, it's not clear whether that was the first potential contamination or if there were even earlier backflows.

Corpus Christi is in the third day of the chemical contamination scare afflicting the city's water system.

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At a news conference Saturday afternoon at City Hall, Mayor Dan McQueen said 30 water samples are being tested in Houston. It's expected those results will be ready sometime Sunday.

He was reluctant to give a timeline for when the water system might be cleared of the chemical contaminant because it's possible the chemical breached the system as early as Dec. 1.

Assistant City Manager Mark Van Vleck said the city has finished flushing about half of the city's dead-end water mains.

The Associated Press reported that an internal email sent Wednesday by Susan Clewis, a regional director for the Texas Commission on Environmental Quality, contained an incident report that described the leak as a "backflow incident from a chemical tank impacting the public water system." It was reported Dec. 7 at a plant run by Ergon Asphalt and Emulsions.

The email doesn't say who initially reported the leak on Dec. 7 or to whom. It says the state environmental agency was notified around 3 p.m. on Wednesday. City officials notified the public that evening.

"Obviously we are concerned about that initial report, that this may have been known for seven days and it may have been going on for that long. And why did it take so long for TCEQ to get notified?" asked Luis Moreno, chief of staff for state Sen. Juan Hinojosa, whose district includes Corpus Christi. "Those are all things that I think are starting to be figured out right now."

McQueen, the mayor of the Gulf Coast city of about 300,000 people, has said local officials also only learned of the leak on Wednesday.

Neither Clewis nor city officials responded to requests from the AP for comment on Friday, when many schools remained closed for a second day.

The TCEQ report indicates that a combination of Indulin AA-86 and hydrochloric acid leaked into the water supply.

Indulin is an asphalt emulsifying agent that's corrosive and can burn the eyes, skin and respiratory tract if a person comes into contact with concentrated amounts. The amber liquid is considered a hazardous material by the Occupational Safety and Health Administration and could cause damage to internal organs.

"You don't expect to see it in water," said Terry Clawson, a spokesman with the Texas Commission on Environmental Quality.

Up to 24 gallons of it may have seeped into a pipeline carrying water, allowing it to move to other areas of the city, Kim Womack, a spokeswoman for the city, said Thursday.

Ergon has said in a statement that it has been in contact with the TCEQ and was "working cooperatively to provide all information to ensure state officials can remedy the situation as quickly as possible." Bill Miller, a company spokesman, declined to explain Friday how a hazardous chemical may have entered the water supply.

Meanwhile, Hilliard Munoz Gonzalez LLP, a Corpus Christi law firm, announced early Saturday that a lawsuit filed against Valero and its subsidiaries and Ergon Aspha & Emulsifiers Inc. by attorney Bob Hilliard has been expanded to a class action suit.

A news release from the firm said that hundreds of Corpus Christi businesses that have had to stay closed because of the water ban have asked to be added to the suit, originally filed on behalf of Coiffures of Country Club Inc., Anthony’s Aveda Concept Salon and Paula Porter.

Contributing: The Associated Press