DIMOCK, Pa. - A consulting firm says it found toxic chemicals in the drinking water of a Susquehanna County community already dealing with methane contamination from natural-gas drilling.

Environmental engineer Daniel Farnham said Thursday that his tests, verified by three laboratories, had found industrial solvents such as toluene and ethylbenzene in "virtually every sample" from water wells in Dimock Township.

Farnham, who has tested water for gas interests and residents, said it would be impossible to say the chemicals were a result of gas drilling.

The chemicals, at least one of which, ethylbenzene, may cause cancer, are among dozens used to hydraulically fracture shale deposits to unlock natural gas thousands of feet underground. The chemicals are also used in an array of products, including paint thinner and gasoline.

The contaminated Dimock wells are in the gas-rich Marcellus Shale, where a rush to tap the vast stores has set off intense debate over the environmental and public health impact of drilling. Millions of gallons of water mixed with numerous chemicals and sand are blasted deep into the earth to free gas from the shale. As much as 90 percent of the mixture is left underground.

Dimock residents sued Cabot Oil & Gas Corp. of Houston last year, alleging the drilling company polluted their wells with methane gas and other contaminants. Pennsylvania's Department of Environmental Protection said defective casings on at least three of Cabot's wells had allowed gas to pollute groundwater. Cabot was fined more than $240,000 and ordered to clean up the pollution.

On Thursday, DEP said it would spend about $10.5 million to provide safe water for the affected Dimock residents, connecting their homes to a municipal water supply in Montrose, about six miles away. The residents balked at an earlier fix that would have placed large, whole-house water-treatment systems in the 14 homes.

DEP chief John Hanger said in an interview that the connection to public water was "the best, and really only, solution," and that if Cabot balked at paying the tab, the state would pay, then go after Cabot for the money.

Officials and residents had discussed another option - drilling a well or wells and piping that water to the homes - but Hanger said it had been dropped because "we don't believe that will ensure a permanent, safe supply of water."

A person who took part in the discussions said Hanger had told residents the entire aquifer might be polluted by gas-drilling operations.

"He said, 'I cannot guarantee that there is any water in the aquifer that is clean today, that will be clean next week, that will be clean six months after the whole system is put in, because of the drilling activity and the damage to the aquifer.' It was repeated twice," said the person, who spoke on condition of anonymity to discuss a private meeting

On Tuesday, 13 families in Lenox Township, about eight miles from Dimock, sued another Houston driller, Southwestern Energy Co., saying their wells were contaminated with fracking fluids. Southwestern denied any problems with its well.

In Dimock, Farnham said, the water samples were tested independently by three labs, all of which showed the same results.

But "can anybody say that this came from fracking, or from frack flow-back? There's no way a true scientist would be able to make that determination based on the data that we have," Farnham said in an interview Thursday. "Until and unless we are able to put a die or marker in the frack liquid, it's going to be awfully difficult to prove irrefutably that it's coming from frack."

Cabot spokesman George Stark said the chemicals had existed in some wells before drilling.

Dimock residents have said that their wells were contaminated shortly after Cabot started drilling near their homes, and that the water from their faucets suddenly became cloudy, foamy, and discolored, and smelled and tasted foul.

Farnham, hired by Cabot in 2008 to perform predrill testing of residential water wells in Dimock, said those tests had not turned up any problems, adding that he had not even tested for the chemicals that Cabot said had existed before drilling.

After the drilling, Farnham was asked by residents to test their water, and was later hired by plaintiffs' attorneys.

"It doesn't take me or any scientist to see some of the impacts on the drinking water," he said. "Your drinking water goes from clear and fine, to a week later being yellow-colored, sediment on the bottom, foam on the top, and an oily smell to it. It's not a figment of anybody's imagination."

The Dimock test results were first reported by the Times-Tribune of Scranton.