RICHMOND, Va. (AP) — The Food and Drug Administration is working to lift the smokescreen clouding the ingredients used in cigarettes and other tobacco products.

In June, tobacco companies must tell the FDA their formulas for the first time, just as drugmakers have for decades. Manufacturers also will have to turn over any studies they’ve done on the effects of the ingredients.

It’s an early step for an agency just starting to flex muscles granted by a new law that took effect last June that gives it broad power to regulate tobacco far beyond the warnings now on packs, short of banning it outright.

Companies have long acknowledged using cocoa, coffee, menthol and other additives to make tobacco taste better. The new information will help the FDA determine which ingredients might also make tobacco more harmful or addictive. It will also use the data to develop standards for tobacco products and could ban some ingredients or combinations.

‘‘Tobacco products today are really the only human-consumed product that we don’t know what’s in them,’’ Lawrence R. Deyton, the director of the Food and Drug Administration’s new Center for Tobacco Products and a physician, told The Associated Press in a recent interview.

While the FDA must keep much of the data confidential under trade-secret laws, it will publish a list of harmful and potentially harmful ingredients by June 2011. Under the law, it must be listed by quantity in each brand.

Some tobacco companies have voluntarily listed product ingredients online in recent years but never with the specificity they must give the FDA, said Matt Myers, president of the Campaign for Tobacco-Free Kids.

For example, Altria Group Inc., based in Richmond and the parent company of the nation’s largest tobacco maker, Philip Morris USA, has posted general ingredients on its Web site since at least 1999.

Cigarette makers say their products include contain tobacco, water, sugar and flavorings, along with chemicals like diammonium phosphate, a chemical used to improve burn rate and taste, and ammonium hydroxide, used to improve the taste.

Scientific studies suggest those chemicals also could make the body more easily absorb nicotine, the active and addictive component of tobacco.

‘‘Until now, the tobacco companies were free to manipulate their product in ways to maximize sales, no matter the impact on the number of people who died or became addicted,’’ Myers said. ‘‘The manner of disclosure previously made it impossible for the government to make any meaningful assessments.’’

About 46 million people, or 20.6 percent of U.S. adult smoke cigarettes, according to the Centers for Disease Control and Prevention, down from about 24 percent 10 years ago. It also estimates that about 443,000 people in the U.S. die each year from diseases linked to smoking.

Tax increases, health concerns, smoking bans and social stigma continue to cut into the number of cigarettes sold, which were estimated to be down about 12.6 percent in the third quarter compared with the same period last year.

Cigarettes and their smoke contain more than 4,000 chemicals; among them are more than 60 known carcinogens, according to the American Cancer Society. But scientists say they can’t yet tell all they’ll learn from the new data because so little is known about how the chemicals combine to affect people.

‘‘The reality is that we have known so little over time that it’s difficult to know with much accuracy what getting a good look is going to tell us about what we could do in the future,’’ said Dr. David Burns of the University of California-San Diego, scientific editor of several surgeon general reports on tobacco.

The real test is whether the FDA acts on the information it receives, said David Sweanor, a Canadian law professor and tobacco expert. Canadian authorities are collecting similar data, but they haven’t taken much action based on it, which is critical, he said. The European Union also has similar submission requirements.

Myers warned that a list of ingredients or an unexplained product label is ‘‘just as likely to mislead as it is to inform’’ if consumers don’t know about the relative effects of ingredients.

Altria has supported what it has called ‘‘tough but fair regulation.’’

But its chief rivals — No. 2 Reynolds American Inc., parent company of R.J. Reynolds, and No. 3 Lorillard, both based in North Carolina — opposed the law. They said it would lock in Altria’s share of the market because its size gives it more resources to comply with regulations and future limits on marketing under the law. Altria’s brands include Marlboro, which held a 41.9 percent share of the U.S. cigarette market in the third quarter, according to Information Resources Inc.