BEND, Ore. -

Bend and Avion Water Co,.officials said Tuesday that it was a water sample from Avion, not the city, that an environmental group tested and found a possible cancer-causing chemical in.

"A study by an environmental group that analyzed drinking water in 35 cities for hexavalent chromium did not test water from the City of Bend?s system," the city said in a statement issued Tuesday afternoon. "The Environmental Working Group (EWG) confirmed that the sample was taken from a private water utility that operates with the city.

Leeann Brown, press secretary for the EWG, told the city in an e-mail: ?I can confirm that the sample was collected in the spring of 2010 by an EWG contact at an address with a utility bill from Avion.? (Avion Water Co. has about 11,500 customers within and surrounding the city)

City officials said Bend follows EPA rules to test for total chromium on a strict schedule for all of its groundwater wells and Bridge Creek surface water.

Looking back at total chromium data to 1987, the city said it has always been below EPA?s maximum contamination level of 100 parts per billion. In fact, the majority of samples tested for total chromium have been ?non-detects.? In other words, no contamination was found, said city spokesman Justin Finestone.

As it turns out, word of the actual water source came after Avion Water officials read of the report on KTVZ.COM and out of curiosity contacted the Environmental Working Group to see if it was their water -- and it was.

Avion gets the water for its 11,500 customers from a dozen groundwater wells and serves residents both inside and outside the city, said Jason Wick, the utility?s executive vice president.

Wick said state labs can only detect the substance down to 1 part per billion, and this amount reported was less than that, ?so our test wouldn?t even have shown up. There?s no lab in the state of Oregon that can test down to that level.?

Wick said they contacted EWG out of curiosity: ?Why wouldn?t I? I?m just as curious as you are what?s in our water.?

However, he added, ?I can?t tell you what a ?significant? level of hexavalent chloride is, because I don?t know.?

He also said there?s no way to tell where the single sample?s chromium 6, as the substance also is known, came from. Experts note that the substance often occurs naturally and is not just a result of industrial processes.

?It may not have come from a well,? he said. ?It may have come from their house?s plumbing. What?s the plumbing made of? Maybe brass, maybe copper? What?s the fitting made of??

?On the one hand, I want to know what?s in the water,? Wick said. ?On the other hand, now I?m being asked to disprove a negative. I can?t test to that level, I don?t know where it comes from -- and yet, I have this test that shows something is in the water.?

Wick?s father, Avion President Jan Wick, stressed that the utility has ?met and exceeded every EPA and (state) Health Division standard.? And he said as soon as Avion learned the water sample came from their utility, and not the city, they notified city officials.

?We have no interest in delivering a product to our customers that?s harmful,? he said. ?For the last two decades, we?ve tested for chromium, and we?ve had none detected. That said, the detection limit was only .005 parts per million. That?s a pretty low level, but way different than 1 part per billion.?

He said water samples already have been taken to see if hexavalent chromium is detected, to the limits of what can be tested at present -- and that the results, expected Thursday, will be provided to customers and also made public, whatever they show.

?We will find out what?s in our water,? Jan Wick promised. ?If there?s Chromium 6 in our water, and it determined in an actionable level, we will do what is required to move that contaminant from the water, should it exist in any life-threatening or health-threatening levels.?

?We don?t think there?s ever been an industry in Bend or surrounding us that uses chromium 6,? he said. ?Chromium occurs naturally. It?s used historically in the U.S. as a rust inhibitor. It?s used a lot in the oil industry, and we don?t have an oil industry here.?

Jan Wick said there are a number of processes that could remove the substance, ?most likely reverse osmosis.?

More from Sunday story about the study:

The Environmental Working Group, in a newly released study, found the substance in 31 of 35 cities sampled.

Monday's report comes as the U.S. Environmental Protection Agency is considering whether to set a drinking water limit for hexavalent chromium , a chemical made famous in the legal case that inspired the movie "Erin Brockovich."

The EPA limits the level of ?total chromium? in drinking water, requiring utilities to test for it. However, that figure includes both trivalent chromium, a mineral humans need to metabolize glucose, and hexavalent chromium, which has caused cancer in laboratory animals.

The environmental group says it chose cities big and small to test, and included places where local water companies already detected high levels of ?total chromium.? Its report was not clear on which cities had municipal or private water sources tested.

Last year, California was the first to limit the amount of hexavalent chromium in drinking water, proposing a ?public health goal? for safe levels of 0.06 parts per billion.