SAN FRANCISCO (AP) — Government auditors say federal officials know nothing about thousands of miles of pipelines that carry natural gas released through the drilling method known as fracking, and need to step up oversight to make sure they are running safely.

Amid the gas-drilling boom, private companies have put in hundreds of small gathering pipelines in recent years to collect new fuel supplies released through the high-pressure drilling technique.

Nationwide, about 240,000 miles of gathering pipelines ferry the gas and oil to processing facilities and larger pipelines in the major energy-producing states. Many of these pipelines course through densely populated areas, including neighborhoods in Fort Worth, Texas.

The Government Accountability Office said in its report issued Thursday that most of those miles are not regulated by the U.S. Pipeline and Hazardous Materials Safety Administration, which means they are not regularly inspected for leaks or corrosion.

In some states, officials don't know where the lines are.

Emily Krafjack, who lives in the gas-rich Marcellus Shale formation in Pennsylvania, said many local residents have no idea that the pipelines near their homes are not overseen by federal regulators. Gathering lines that run in the rural northeastern corner of the state receive no federal oversight if there are fewer than 10 homes within 220 yards of the pipeline.

"Who would ever think that they could run something like this next to your home and it wouldn't have any regulations attached to it?," said Krafjack, a former community liaison for Wyoming County, Pa., on gas issues.

Nationwide, there are about 200,000 miles of gas gathering lines and up to 40,000 miles of hazardous liquid gathering lines in rural and urban areas alike, ranging in diameter from about 2 to 12 inches. But only about 24,000 of those miles are regulated, according to the report.

The industry is not required to report pipeline-related fatality, injury or property damage information about the unregulated lines. PHMSA only collects information about accidents on the small subset of gathering lines that the agency regulates, but that data was not immediately available Thursday.

The pipeline agency is considering collecting more data on the unregulated gas gathering lines, but the plans are still preliminary and have met with some resistance from the natural gas industry. Agency officials are reviewing more than 100 public comments received about their proposal for gas lines, and also plan to propose a rule that will cover hazardous liquid gathering pipelines by the fall, said Jeannie Layson, a spokeswoman for the Pipeline and Hazardous Materials Safety Administration.

PHMSA delegates some enforcement of its rules to state-level pipeline safety authorities, who the Government Accountability Office surveyed to understand the array of risks associated with gathering lines.

Those state-level agencies told the auditors that construction quality, maintenance practices, unknown locations, and limited or no information on current pipeline integrity all posed safety risks for federally unregulated gathering pipelines.

The expansion of hydraulic fracturing, which involves shattering rock thousands of feet underground with a combination of water, sand and chemicals, promises staggering yields, and drilling also comes with promises of job creation and economic opportunities.

But in Fort Worth, where dozens of new gathering lines have been laid in recent years to capture supplies from hundreds of new wells, some residents say there aren't enough protections from leaks and ruptures due to corrosion.

"It's ridiculous," said Jerry Lobdill, a retired chemical engineer who lives in a Fort Worth neighborhood near several new gas wells and has several lines running near his home. "The gathering lines are unregulated, the city doesn't know where they are, and they're buried so you can't see them."

The recent surge in drilling also has led California lawmakers to write new laws to increase oversight of the industry.

Assemblyman Bill Wieckowski, D-Fremont, is sponsoring a bill now pending before a state Senate committee that would require gas and oil producers to disclose what chemicals they are using when they engage in hydraulic fracturing.

"If we're on this cusp of a boom then maybe we at the very least need to know where these lines are," Wieckowski said.