NEW YORK (AP) — Two U.S. senators on Friday again called on federal regulators to close what they say are loopholes that allow energy-drink makers to sell products with additives and high levels of caffeine that the lawmakers say have not been proven safe.

The letter to the Food and Drug Administration from Sens. Dick Durbin, D-Ill., and Richard Blumenthal, D-Conn., comes after the agency said this week that it is investigating reports of five deaths in which the consumption of Monster drinks was cited.