ALBANY — The state’s Health Department found in an analysis it prepared early last year that the much-debated drilling technology known as hydrofracking could be conducted safely in New York, according to a copy obtained by The New York Times from an expert who did not believe it should be kept secret.

The analysis and other health assessments have been closely guarded by Gov. Andrew M. Cuomo and his administration as the governor weighs whether to approve fracking. Mr. Cuomo, a Democrat, has long delayed making a decision, unnerved in part by strident opposition on his party’s left. A plan to allow a limited amount of fracking in the state’s Southern Tier along the Pennsylvania border is still seen as the most likely outcome, should the drilling process receive final approval.

The eight-page analysis is a summary of previous research by the state and others, and concludes that fracking can be done safely. It delves into the potential impact of fracking on water resources, on naturally occurring radiological material found in the ground, on air emissions and on “potential socioeconomic and quality-of-life impacts.”

But it remains difficult to discern how much original research the state has done on potential health impacts, and environmentalists worry that the administration’s lack of transparency is hiding a lack of rigor in its assessment of public health risks. At the same time, the drilling industry, and landowners who have leased their land in the Southern Tier, have grown increasingly frustrated with delays by the Cuomo administration to announce a final plan. State regulators have now been studying the issue of fracking for about four years.