ALBANY, N.Y. — Handing environmentalists a breakthrough victory, New York plans to prohibit fracking for natural gas because of what regulators say are its unexplored health risks and dubious economic benefits.

New York, which overlies part of the gas-rich Marcellus Shale formation that has led to a drilling boom in Pennsylvania and other nearby states, has banned shale gas development since 2008, when the state began an environmental review of hydraulic fracturing.

The announcement, though not final, means a ban is all but etched in stone.

“Never before has a state with proven gas reserves banned fracking,” said Deborah Goldberg, an attorney with Earthjustice, adding that the decision “will give courage to elected leaders throughout the country and world: Fracking is too dangerous and must not continue.”