CHICAGO (CBS) — Hundreds of homes in University Park have now been under a “do not consume” advisory for their tap water for the past 20 nights after their water utility company, Aqua Illinois, discovered alarming lead levels in some homes.

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“We have evidence that the situation is improving, and while we have been able to remove many homes from the do not consume advisory, it could be a few more weeks until this issue is completely resolved,” the company said in a statement Tuesday.

Aqua Illinois said people in about 1600 homes currently under the advisory should not drink their water or use it to cook or brush their teeth.

The company initially said it issued the widespread advisory out of an abundance of caution after finding alarming lead levels in just 15 homes. It continued testing and now says it’s found 21 homes with high lead levels.

Aqua said a treatment product it used may have caused lead to dissolve into the University Park water from older pipes and fixtures. They have switched to another product. It is unclear whether any of the elevated lead levels in homes were detected after the switch.

“What is going on?” University Park resident Sarah Boyd said. “Where are we at in the process? I need to know so I can have some comfort here.”

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Boyd, who said she couldn’t host her Fourth of July party because of the advisory, is still waiting for Aqua to let her know whether there is lead in her water. The company says it is still testing homes.

“It is impossible (to host the party) because there are children, and you know they’re going to run in, get some water,” Boyd said. “I just don’t trust it.”

Boyd boiled her eggs with bottled water Thursday.

Aqua said it has handed out thousands of cases of bottled water to residents. Its information center was also open for four hours Thursday, where residents could pick up free bottled or filtered water.

“I can’t carry a five gallon jug of water, and then I don’t trust the water,” Boyd said. “I don’t know where they’re getting the water from.”

The company released the following statement Thursday:

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“Aqua understands the inconvenience this has caused to impacted customers and we have been working everyday to restore safe drinking water as quickly as possible. Customers that were under the do not consume advisory at anytime will receive a full credit for June billing. Moving forward, customers will not be billed for water they can not consume. While we are working to remove homes from the do not consume advisory, customer safety remains our top priority and water testing and treatment takes time. We have evidence that the situation is improving and while we have been able to remove many homes from the do not consume advisory it could be a few more weeks until this issue is completely resolved. In the meantime, we have distributed more than 25,000 cases of water, 755 water faucet filters, 2,500 water filter pitchers and hundreds of free water testing kits. Aqua has opened an information center to answer questions and provide resources to our customers. We will continue to work with the Mayor and regulators to restore safe drinking water as soon as possible. We would like to apologize for this inconvenience and thank our customers for their patience.”

Tim McNicholas