ALLENTOWN, Pa. — The U.S. Environmental Protection Agency announced Thursday that it will deliver fresh water to four homes in a northeastern Pennsylvania village where residential water wells were tainted by a gas driller. It also said it will begin testing the water supplies of dozens more homes as it ramps up its investigation more than three years after homeowners say the water supply was ruined.

Capping a tumultuous two weeks in which the EPA first promised the residents a tanker of water — and then quickly backed away, saying more study was needed — federal environmental regulators said they have concluded that contaminant levels in four of the homes pose a health hazard.

Additionally, the agency announced that it's expanding its investigation in Dimock, a tiny crossroads at the center of a national debate over gas drilling and the extraction technique known as hydraulic fracturing, or fracking. EPA said it will sample water at about 60 homes in the area of Carter and Meshoppen roads "to assess further whether any residents are being exposed to hazardous substances that cause health concerns."

More than a dozen homeowners in Dimock say they have been without a reliable supply of clean water since Cabot Oil & Gas Corp., the Houston-based drilling firm blamed for polluting their aquifer, stopped making daily deliveries on Nov. 30. EPA said its review of existing data supplied by residents, Cabot and state environmental regulators didn't "support the need for alternative water" for the other homes, pending the results of the EPA's own testing.

"EPA is working diligently to understand the situation in Dimock and address residents' concerns," EPA Regional Administrator Shawn M. Garvin said in a statement. "We believe that the information provided to us by the residents deserves further review, and conducting our own sampling will help us fill information gaps. Our actions will be based on the science and the law and we will work to help get a more complete picture of water quality for these homes in Dimock."

It's not clear how many wells in Dimock were affected by the drilling, which began in 2008. The state has found that at least 18 residential water wells were polluted.

Cabot, which was banned in 2010 from drilling in a 9-square-mile area around the village, took legal responsibility for the Dimock methane contamination but contends that water wells in the area were tainted with methane long before the company arrived. The company also says it met a state deadline to restore or replace Dimock's water supply, installing treatment systems in some houses that have removed the methane. The state Department of Environmental Protection allowed the company to stop paying for replacement water.

But 11 homeowners who are suing Cabot say their wells are still tainted with methane gas and toxic chemicals that are used in fracking, a technique in which water, sand and chemicals are blasted deep underground to free natural gas from dense rock deposits.

EPA's decision to intervene in Dimock is unlikely to sit well with Pennsylvania's environmental chief, Michael Krancer, who has accused the EPA of having only a "rudimentary" understanding of the situation there. Krancer, a frequent EPA critic who serves under pro-drilling GOP Gov. Tom Corbett, urged Garvin in a letter released publicly last week to allow any EPA probe to "be guided by sound science and the law instead of emotion and publicity."