Thousands of homeowners in the U.S. are finding out the hard way that so-called “mineral rights” for fossil fuel deposits that may exist beneath their newly purchased property have already secretly been sold to gas and drilling companies, effectively nullifying their ability to object to fracking or other extraction projects that could have serious health impacts on them or their families.

Acording to a new Reuters special report published Wednesday:

According to the report—which cites the current nationwide oil and gas fracking boom—home builders and developers have found it increasingly lucrative to separate and withhold mineral rights from land deals, often without full disclosure, and instead sell those rights to fossil fuel companies.

“Home-builders and developers have been increasingly – and quietly – hanging on to the mineral rights underneath their projects, pushing aside homeowners’ interests to set themselves up for financial gain when energy companies come calling,” Reuters writes.

Several states such as Texas and Oklahoma have for a long time allowed the severing of mineral rights from land rights. However, the practice is growing across the country—particularly since “once-inaccessible stores of oil and gas,” which have remained trapped beneath “bustling urban neighborhoods and tree-shaded suburbs in places like Denver and Los Angeles,” have now been made accessible by fracking technology.

“Homeowners in these ‘virgin locations’ are often untutored in the nuances of property rights,” Reuters writes, “and unaware they may be sitting atop oil and gas deposits that could be worth thousands or even millions of dollars.”