The U. S. Food and Drug Administration announced Wednesday that preliminary analysis of popular smoking devices known as electronic cigarettes have shown them to contain carcinogens and other toxic chemicals dangerous to humans.

The FDA's findings are in direct contradiction to claims by electronic cigarette manufacturers who tout their products to be a "healthy way" to smoke and contain little more than water vapor, nicotine and propylene glycol which is used to create artificial smoke in theatrical productions. These "e-cigarettes," are battery-operated and spiced with flavors such as chocolate, cola or bubble gum, and when heated, the liquid produces a vapor that users inhale.

Joshua Sharfstein, the F. D. A.'s principal commissioner said, "We're concerned about them because of what we know is in them and what we don't know about how they affect the human body."

Federal health officials said the devices turn nicotine, which is highly addictive, and other chemicals into a vapor that is inhaled by the user. Dr. Margaret A. Hamburg, commissioner of the FDA said, "The FDA is concerned about the safety of these products and how they are marketed to the public."

The tests were undertaken as e-cigarettes have not been submitted to the FDA for evaluation or approval, and the agency had no way of knowing the levels of nicotine or the amounts or kinds of other chemicals that these products contained.

19 varieties of cartridges, which hold the liquid and two cigarettes, one manufactured by NJoy and another by Smoking Everywhere were analyzed by the FDA. The analysis found that several of the cartridges contained detectable levels of nitrosamines, tobacco-specific compounds known to cause cancer. One Smoking Everywhere cartridge was found to contain diethlyene glycol, a common ingredient in antifreeze that counterfeiters have substituted for glycerin in toothpaste, killing hundreds worldwide.

Dr. Sharfstein said the agency was "not sure" what type of effect the diethlyene glycol and other carcinogens have on the human body when inhaled through electronic cigarettes.

The analysis found nicotine levels varying even in cartridges whose labels claim to have the same amount of nicotine while some of the cartridges that claimed not to contain nicotine actually did.

In a statement the Electronic Cigarette Association, an industry trade group, said that the F. D. A.'s testing was too "narrow to reach any valid and reliable conclusions" and that its members sell and market their products only to adults.

A statement from the chief executive officer of NJoy, Jack Ledbetter, said a third party had tested its products and found them to be "appropriate alternatives" for cigarettes. The company said its experts would review its tests and the F. D. A.'s.

The F. D. A. has called electronic cigarettes drug delivery devices and said they should not be allowed in the country. Their worry is that electronic cigarettes, which are offered in different flavors, are enticing to children and may be easy for those under 18 to obtain online or in malls.

The agency would not comment on whether it planned to ban or seize the devices.

"Children who use these products may also be using other tobacco products," said Dr. Matthew McKenna, director of the Office of Smoking and Health, Centers for Disease Control and Prevention. "It's a good idea to make sure the child is aware of the dangers of tobacco in products in general."