Oil and gas drillers ran afoul of regulators on average 2.5 times a day in three energy-intensive states for mistakes such as wastewater spills, well leaks and pipeline ruptures during the boom in hydraulic fracturing.

Online records in West Virginia, Pennsylvania and Colorado showed regulators issued 4,600 citations from 2008 to 2013, the Natural Resources Defense Council said Thursday in a report. The report excluded violations in 33 other states with drilling because such records aren’t available on the Internet.

“It’s extremely difficult for the public to get this kind of information,” said Amy Mall, an author of the report for the New York-based environmental advocate. “The companies are violating the law too often, and we need policy solutions to increase transparency and to change the consequences for not complying” with the rules, she said.

Hydraulic fracturing has sparked a producing boom in long- bypassed energy states such as Pennsylvania, site of the first U.S. oil well. The technique lets producers break apart the underground shale formations and free trapped oil or gas. Each job can entail millions of gallons of water with sand and chemicals. The industry says the practice is safe, and fracking itself hasn’t caused chemical contamination of water supplies.

The NRDC report tabulated citations issued by inspectors for breaching rules adopted to make sure wells are constructed soundly and the wastewater is handled safely. The vast majority of violations -- 4,053 -- were in Pennsylvania. West Virginia and Colorado combined had about 600.

In addition, 1,933 spills were reported in Colorado, although most weren’t listed as violations.

The report doesn’t categorize the infractions, but lists examples such as poor well construction and a ruptured pipeline. The report found the number of violations wasn’t directly linked to the number of wells.

Pressure from groups such as the NRDC for more disclosures about fracking comes as drillers grapple with a drop in oil and gas prices, and increasing regulation from the federal government for production on federal lands. Oil prices dropped about 50 percent in the past year through Wednesday, while gas fell 39 percent.