EVANS CITY, Pa. (AP) — A western Pennsylvania woman says state environmental officials refused to do follow-up tests after their lab reported her drinking water contained chemicals that could be from nearby gas drilling.

At least 10 households in the rural Woodlands community, about 30 miles north of Pittsburgh, have complained that recent drilling impacted their water in different ways.

The Department of Environmental Protection first suggested that Janet McIntyre’s well water contained low levels of only one chemical, toluene. But a review of the DEP tests by The Associated Press found four other volatile organic compounds in her water that can be associated with gas drilling.

DEP spokesman Kevin Sunday said on Friday that the low chemical concentrations were not a health risk, and suggested that the contamination may have come from the agency’s laboratory itself or from abandoned vehicles on or near the property. But Sunday didn’t answer why DEP failed to do follow-up tests if the DEP suspected that its own lab was contaminated.

One public health expert said the lack of follow-up tests by DEP doesn’t make sense.

“DEP cannot just simply walk away,” said Dr. Bernard Goldstein, professor emeritus at the University of Pittsburgh School of Public Health.

McIntyre and other residents say the water problems started about a year ago, after Rex Energy Corp. of State College, Pa., drilled two wells. But a map Rex provided also shows gas wells from other companies in the area.

Residents in the community have been complaining for nearly a year, but DEP never revealed the possible presence of chemicals to the general public.

Rex has been supplying drinking water to many households, but has sent letters notifying them it will no longer deliver drinking water after Feb. 29.

McIntyre’s water showed detectable levels of t-Butyl alcohol, acetone, chloromethane, toluene and 1, 3, 5-trimethylbenzene. The chemicals can be used in the high-pressure hydraulic fracturing process that has led to a production boom of deep shale gas in Pennsylvania. But some are also commonly used in households and other industry, such as toluene, a paint thinner.