The Food and Drug Administration on Tuesday began using one of the key powers Congress gave it under the landmark 2009 tobacco-control law: Final say over which new tobacco products can be marketed and sold to consumers.

The Family Smoking Prevention and Tobacco Control Act gave the FDA broad authority to regulate everything from cigarettes to smokeless tobacco. Before its passage, companies could introduce new products without the blessing of any federal regulator.

Since the law’s enactment, the FDA has received roughly 4,000 applications for products that companies claimed were “substantially equivalent” to ones already on the market, but the agency had not acted on any of them.

Until Tuesday.

The FDA said it had approved applications for two types of non-menthol cigarettes made by Lorillard after determining that the cigarettes, while slightly different than previous products, wouldn’t pose new public health worries.

The FDA rejected four other applications, citing potential new health concerns raised by some ingredients and a lack of detail about product designs. It said companies had withdrawn another 136 applications.

The agency declined to name the specific companies or products.

Tuesday’s move put hardly a dent in the backlog of tobacco-product applications before the FDA. Some have been awaiting a ruling for more than two years.

But it does mark a turning point in the long-running fight over tobacco regulation.

“This is an historic step forward,” said Mitch Zeller, director of the FDA’s Center for Tobacco Products. “Today is the first day that a regulatory agency anywhere in the world has made a science-based determination, on a pre-market basis, that a product either can or cannot be marketed.”

FDA Commissioner Margaret Hamburg told reporters that the announcement represents an “important step toward the FDA’s goal of reducing preventable disease and death caused by tobacco.”

She added, “For the first time, the federal government is bringing science-based regulation to the manufacturing, marketing and distribution of tobacco products.”

The law allowed thousands of products introduced between February 2007 and March 2011 to remain on the market, pending review by the FDA. About 500 products submitted for review after March 2011 cannot be sold until the FDA approves them.

Zeller emphasized that Tuesday’s approvals do not mean that the FDA considers the products “safe” or “FDA-approved” — only that they don’t raise new health concerns. He also said he expects the agency to pick up the pace of its decisions.

“We are proud to be the first company in the industry to receive authorization to begin marketing these new products in the U.S. through the FDA’s substantial equivalence pathway,” Lorillard’s chief executive, Murray Kessler, said in a statement. He added, “[We] believe that the FDA has carried out its evaluation process in a deliberate manner reflecting sound science.”

Tobacco-control advocates reacted with cautious optimism, praising the FDA for its apparent rigor in examining the potential dangers of new tobacco products. But they also urged the agency to provide more details about the criteria it is using to decide whether to approve products and what information tobacco companies have provided.

“It is an important milestone,” said Matthew Myers, president of the nonprofit Campaign for Tobacco-Free Kids. “But the information disclosed leaves many unanswered questions. . . . Without that information, it is impossible to assess the impact of these decisions.”