HARRISBURG, Pa. (AP) — Pennsylvania regulators halted work Monday at dozens of unfinished natural gas wells being drilled by the company whose out-of-control well spewed out explosive gas and polluted water for 16 hours last week.

The order against Houston-based EOG Resources Inc. will remain in place until the Department of Environmental Protection can finish its investigation and until after the company makes whatever changes may be needed, Gov. Ed Rendell said.

The order stops EOG from drilling and hydraulically fracturing wells. It affects about 70 unfinished EOG wells into the gas-rich Marcellus Shale formation.

Another concern was the apparently bungled attempts to notify the right emergency-response officials about the accident. Fines are likely, said Environmental Protection Secretary John Hanger.

Nobody was hurt in Thursday's blowout in a heavily forested section of north-central Pennsylvania. The accident shot highly pressurized gas and wastewater as high as 75 feet. The gas never caught fire, but state officials had worried about an explosion and ordered electrical service to the area cut before specialists secured the well at about noon Friday.

About 35,000 gallons of wastewater have been pumped into holding tanks so far, the company said.

Monitors in a nearby spring show signs of pollution, although Hanger said the spring is in such a rural area that it is not viewed as a public health hazard. Officials say they have detected no pollution in larger waterways that feed public water supplies.

The state says the company is cooperating and is supportive of the stop-work order.

Gary L. Smith, vice president and general manager of EOG's Pittsburgh office, said the company regrets the accident and would continue to work with Pennsylvania officials.

"After the investigations are complete, we will carefully review the findings with the goal of enhancing our practices," Smith said. "When all outstanding issues are resolved, we look forward to resuming full operations in Pennsylvania."

DEP officials said the well's blowout preventer failed, and they were investigating whether the failed equipment was the primary cause.

A blowout preventer is a series of valves that sit atop a well and allow workers to control the pressure inside. Hanger and EOG said the blowout preventer had been tested successfully by the company on Wednesday morning.

The company had blasted a million gallons of water, sand and chemicals underground to shatter tightly compacted shale and release trapped natural gas, according to the DEP. The process is known as hydraulic fracturing, or fracking.

The solution contained biocide, which kills organisms, and a scale inhibitor that are considered by their makers toxic enough to inflict serious damage on someone if consumed, according to material safety data sheets provided Monday by the DEP. Industry officials, however, say only tiny amounts of those chemicals are used.

In addition, the briny wastewater that returns after being pumped thousands of feet into the earth can kill fish and other aquatic life if enough of it saturates a waterway.

Eight workers were close to completing the well when they lost control of it and had to evacuate the site at 8 p.m. Thursday.

Hanger said EOG tried to notify the DEP, but contacted an employee who was on vacation and not part of the agency's emergency response.

A Clearfield County emergency management official, Jerry Pollock, said Monday that a 911 dispatcher first heard from EOG at 11 p.m., but was told it was a "small problem and it was being handled."

The county reported it to the Pennsylvania Emergency Management Agency in a routine conference call about an hour later, Pollock said. The agency notified DEP after that.