BOSTON (AP) — Congressman Edward Markey is calling on a dozen energy drink companies to provide more information about their ingredients and marketing claims.

Markey and Senate Democrats Dick Durbin of Illinois and Richard Blumenthal of Connecticut sent the letters to companies including Red Bull, Pepsi, and Monster.

A new government survey suggests the number of people seeking emergency treatment after consuming energy drinks has doubled nationwide during the past four years from 10,000 to 20,000 visits.

Markey said the firms need to be clear about what they think their product is, what it contains, and what it can do.

The industry says its drinks are safe and there's no proof linking its products to the adverse reactions.

Markey is the only Democrat to announce he'll run for John Kerry's Senate seat if Kerry becomes secretary of state.