WASHINGTON -- The American Medical Association called for a ban on the weight loss supplement Ephedra on Tuesday, and a top maker of the supplements said the industry should be more closely regulated.

When misused, Ephedra can cause heart attacks and can kill even strong, healthy people, witnesses told a hearing of the Senate Subcommittee on oversight of government management, restructuring, and the District of Columbia.

The hearing is one of several being held while the U.S. government ponders whether to restrict the supplement, which can be sold freely over the counter under current laws.

But the government is at the same time cracking down on some makers. On Monday, the U.S. Food and Drug Administration said it had warned a Dutch-based Internet company about its website selling yellow jackets, an Ephedra-containing herbal product, as an alternative to illicit street drugs.

On Tuesday Health and Human Services Secretary Tommy Thompson said he had asked the FDA to recommend the "strongest possible mandatory warning label" for Ephedra products.

Ephedra, also known as Ma Huang, is virtually the same ingredient as the pseudoephedrine found in many over the counter decongestants.

Companies that promote its use as a weight loss supplement say it can speed metabolism, helping users burn off calories.

But these same qualities can cause heart rhythm defects, says the American Medical Association.

Not Recommended for Weight Loss "Diet aids containing Ephedra are not recommended for weight loss," Reuters quoted the AMA's Dr. Ron Davis as telling the Senate Subcommittee hearing. "And because of Ephedra's effects on the cardiovascular and central nervous systems, it may cause cardiac arrhythmias, heart attacks, strokes, seizures and sudden death in both previously healthy people, as well as in those with risk factors for these conditions."

Davis said people assume the supplements are safe, because they are classified as foods.

"Dietary supplements containing Ephedra have significant may be serious or fatal to people with preexisting illnesses, as well should be removed from the market," he said.

Dr. Sidney Wolfe, of the consumer organization Public Citizen's Health Research Group, agreed.

"This is not and has never been a question of scientific or medical evidence. It is a question of politics, and the extraordinarily dangerous political cowardice of the FDA and HHS secretary Thompson in the face of massive lobbying by Ephedra-makers in Washington," Wolfe told the hearing.

Kevin Riggins of Lincoln, Illinois said his 16-year-old son, Sean, died last month after taking Yellow Jackets.

"When the coroner told us that Sean had died of a heart attack, it did not seem possible. Sixteen-year-old children in good physical health don't just up and die of a heart attack," he said. "This product is just one step away from being dispensed from a candy machine next to the Lions Club mints," added his wife, Debbie Riggins. "We need to take action to see that children can't access such deadly candy."

Even the industry said the products need to be more closely regulated. Metabolife's proposal includes a prohibition on the promotion of Ephedra products as alternatives to illicit drugs," David Brown, president and chief executive officer of Metabolife International, Inc., a leading maker of ephedrine supplements, told the committee.

He would also propose banning sales of such products to anyone under the age of 18.