Cans of Monster Beverage energy drinks. (David Paul Morris/BLOOMBERG)

As the Food and Drug Administration continues to investigate the safety of energy drinks, two of the biggest makers of energy beverages are shelling out tens of thousands of dollars to pay Washington lobbyists.

Since November, Monster Energy has spent $100,000 to lobby on “legislation and oversight regarding energy drinks.” The Corona, Calif.-based beverage maker retained lobbyists at Washington law firm Covington & Burling — including Dan Bryant, head of the firm’s government affairs group and a longtime lobbyist for PepsiCo — on Nov. 13, but it was not made public until the firm filed year-end lobbying reports due last week to the Senate Office of Public Affairs. Covington has represented Monster on food compliance issues for several years. The company declined to comment.

Red Bull North America has hired Podesta + Partners, the lobby firm run by power broker Heather Podesta, to “educate policymakers regarding energy beverages,” according to Senate records. Since hiring the firm on Nov. 26, Red Bull has spent $20,000 on lobbying. Neither Red Bull nor Podesta + Partners returned a request for comment. Podesta’s firm has previously lobbied for the American Beverage Association, which encourages beverage makers to label energy drinks with caffeine content and discourages the sale of energy drinks at K-12 schools.

Red Bull also retained lobbyists at the Washington law firm Olsson Frank Weeda Terman Matz on Nov. 30 to “advise, consult and advocate regarding beverage regulation,” though they have yet to pay the firm any fees.

It is the first time either company has hired outside lobby firms.

Scrutiny of energy drinks, which contain caffeine, intensified last fall after Sen. Dick Durbin (D-Ill.) and Sen. Richard Blumenthal (D-Conn.) pressed the FDA to look into stricter regulation of the level of caffeine in energy drinks. A spokeswoman for the agency said last week that the investigation is ongoing.

Between 2004 and October 2012, 17 people died and more than 100 had chest pains, cardiac arrest and other health problems after consuming 5-Hour Energy, Monster and Rockstar beverages, according to FDA data. The FDA noted that the reports do not mean the drinks necessarily caused those ailments.