Story highlights Restrictions lifted after water sample testing, Texas environmental agency says

Some residents had not been able to use tap water in their homes for four days

(CNN) All water restrictions have been lifted in Corpus Christi, Texas, authorities said Sunday.

The announcement came after 28 water samples were tested and none came back positive for unacceptable levels of Indulin AA-86, the Texas Commission on Environmental Quality said in a news release.

Indulin AA-86 is an asphalt emulsifier. It apparently got into the water system through "a third party," Mayor Dan McQueen said.

The restrictions were lifted Sunday in two sections of the city that serve more than 250,000 people. The third section was cleared to begin using water again on Friday.

Seven reports of health symptoms related to use of prohibited water have not been confirmed, the news release said.

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