ALBANY, New York - On Monday, protesters poured into a hearing room in Albany, New York to make the case that the state should not lift a moratorium on hydraulic fracturing - better known as "fracking" - later this month.

Their overriding message: There is no evidence that fracking, the controversial process of extracting oil and natural gas from huge underground rock formations, is safe.

"As of yet, there has been no study that satisfies any of the concerns that people have in New York," said Travis Proulx of Environmental Advocates of New York. "We have no answers here in New York on the public health, economic or environmental impacts."

That isn't to say, of course, that there haven't been studies done on the issue. But in the fraught debate over fracking, it isn't always easy to decide which ones to trust, and how much to trust them.