Caffeine powder, sold as a dietary supplement, is dangerous and should be better regulated, according to lawmakers and consumer groups.

One teaspoon of caffeine powder is equal to between 16 and 25 cups of coffee. Ten grams—about a tablespoon—can be deadly for an adult. The powder can be purchased online and in some retail stores, The New York Times reports. Although the packages often contain warning labels, they are voluntary, the article notes.

A 100-gram package contains as much caffeine as 400 “tall” cups of Starbucks coffee, 1,250 Red Bulls or 3,000 cans of Coke. It costs about $10, according to the newspaper.

In December 2014, the Food and Drug Administration (FDA) issued a warning about powdered pure caffeine, following the deaths of at least two young men who used the product. “Pure caffeine is a powerful stimulant and very small amounts may cause accidental overdose. Parents should be aware that these products may be attractive to young people,” the FDA warned in a statement.

The agency asked companies that sell powdered caffeine to voluntarily take the product off the market. A spokeswoman for the FDA said that although the federal government has not restricted the sale of powdered caffeine, the agency “will consider taking regulatory action, as appropriate, to protect consumers.”

Caffeine overdose symptoms can include rapid or dangerously erratic heartbeat, seizures and death. Other symptoms include vomiting, diarrhea, stupor and disorientation. The symptoms are likely to be much more severe in people who use caffeine powder than in those who drink too much coffee, tea or other caffeinated beverages, according to the FDA.

In January, six U.S. senators asked the FDA to ban retail sales of pure caffeine. The Illinois and Ohio Senates approved bills last month banning retail sales of caffeine powder. Similar bills have been introduced in New York, New Jersey and Maryland.