WASHINGTON -- The parents of an Ohio teen who died from an overdose of caffeine powder are urging federal regulators to ban sales of the stimulant, saying that children must be protected from a highly potent substance.

Dennis and Katie Stiner, of LaGrange, Ohio, were in Washington on Tuesday on behalf of their 18-year-old son Logan, who died in May after ingesting about 23 times the amount of caffeine found in a typical coffee or soda drink.

"Before May 27, 2014, we had never heard of `caffeine powder.' Now we think about it every day," the Stiners said in a meeting with lawmakers.

As little as a single teaspoon of the stimulant can be fatal.

The Stiners said the Food and Drug Administration must do more to keep teens and young adults away from pure powdered caffeine, which is marketed as a dietary supplement primarily on the Internet and largely unregulated, unlike caffeine added to soda.

In July, the FDA cautioned consumers to avoid caffeine powder as it considers possible regulatory action. The powder remains available for sale online even as the agency acknowledges it often lacks adequate warning labels and that people can easily take a lethal amount.

The Stiners met with Sens. Sherrod Brown, D-Ohio, and Richard Blumenthal, D-Conn., and were joined by Jim and Julie Sweatt, the parents of Wade, a 24-year-old Georgia resident who also died after ingesting caffeine powder.

"We must do everything we can to get this product off the market and away from children," the Stiners said.

Brown and Blumenthal pledged to continue pressing the FDA to ban the product and said they will consider legislative action if necessary.

"While the dangers are not broadly understood, powdered caffeine is widely available online or in stores with little warning or guidance. That must stop," Brown said. "While it's too late to save Logan and Wade from this dangerous substance, we must act quickly before more lives are lost."

Blumenthal called the stimulant a poison. "There ought to be a great big `skull and bones' on it, or it should be banned," he said.

In a statement Tuesday, the FDA said it was continuing its investigation and noted that since its July warning to consumers, some online retailers have discontinued selling caffeine powder. The agency did not indicate how long its review may take or what regulatory action it was considering.

Because caffeine powder is sold as a dietary supplement, it's not subject to the same federal regulations as certain caffeinated foods. Users add it to drinks for a pick-me-up before workouts or to control weight gain, but it is almost impossible to measure with common kitchen tools, according to the FDA.

A mere 1/16th of a teaspoon can contain about 200 milligrams of caffeine, roughly the equivalent of two large cups of coffee.

In the case of Logan Stiner, a wrestler, an autopsy found that he had more than 70 micrograms of caffeine per milliliter of blood in his system, as much as 23 times the amount found in a typical coffee or soda drink, when he died at his home. Symptoms of caffeine overdose or toxicity include rapid or erratic heartbeat, seizures, vomiting, diarrhea and disorientation.

Stiner's parents described the teen, who died days before his high school graduation, as a bright kid who was looking forward to attending the University of Toledo to study chemical engineering.

"It was tragic," his mother told senators. "He had a busy week and he thought it wouldn't hurt."