WASHINGTON - Three members of Congress are asking more than a dozen energy drink companies to explain their rationale for marketing their energy drinks and to provide data about their ingredients and claims in marketing campaigns.

The letters, sent by Rep. Ed Markey (D-MA) and Senators Dick Durbin (D-IL) and Richard Blumenthal (D-CT), were sent to energy drink makers last week and follow up on previous letters sent by the lawmakers to the Federal Trade Commission (FTC) and Food and Drug Administration (FDA) as they continue their investigations into the safety, ingredient disclosure and marketing of energy drink products.

"Energy drink companies need to be clear with consumers about what they think their product is, what it contains, and what it can do," said Rep. Markey, who previously asked the FTC to investigate the claims of energy drinks. "The broad claims made by these products and their blurred classification in the marketplace make it difficult for consumers, particularly young consumers, from making informed decisions about their consumption."

The energy drink industry has come under increasing scrutiny after a recent FDA release of several reports of deaths and injuries in which the drinks were mentioned and among new data showing a rise in emergency room visits for complications related to caffeinated energy drinks. In a press statement, the lawmakers cite a new survey of hospitals that says emergency room visits from 2007 to 2011 related to energy drink consumption doubled from 10,000 to 20,000 visits.

"As new products and new patterns of energy drink use are emerging, we are working closely with the FDA to strengthen our understanding of the potential health impact of these products. Energy drink companies can partner in our effort by being forthcoming about the ingredients in their products and the processes they use to determine those ingredients are safe," said Sen. Durbin, who first called for the FDA to investigate energy drinks in April 2012 following the death of 14 year-old Anais Fournier.

"There is very clearly a lack of understanding about the health effects of energy drinks and their ingredients especially on children and adolescents," said Sen. Blumenthal, who has also been investigating energy drinks and FDA oversight. "Energy drink makers are mistaken if they believe they have escaped regulatory oversight to safeguard consumer health."

In the letters, the three lawmakers ask energy drink companies to answer whether they believe their products are conventional food products or dietary supplements. As the letter notes, while the FDA has the authority to regulate both conventional foods and dietary supplements, the requirements for ingredients, manufacturing processes, reporting of adverse events, and labeling differ depending on whether the product is marketed as a beverage or as a supplement.

The letters also ask for ingredients and amounts of stimulants like caffeine and guarana, and for studies that back up health or other claims made in the marketing of the products.