Another prominent voice joined hockey's player-safety debate Thursday when United States Senator Richard Blumenthal (a Democrat from Connecticut) sent a letter to NHL commissioner Gary Bettman demanding the league clarify recent comments that "appear dismissive about the link between head trauma and chronic traumatic encephalopathy (CTE) in the game of hockey."

Blumenthal is the ranking member of the Senate's Consumer Protection subcommittee, which has jurisdiction over professional sports.

In a letter dated June 23 and released by the senator's office, Blumenthal takes the NHL to task for not taking seriously "the prevalence and danger of concussions in the sport" and asks nine pointed questions of Bettman, all of them relating to the NHL's handling of concussions in the sport.

The NHL declined to comment on Blumenthal's letter, which "respectfully" requested Bettman respond within a month.

The NHL is already under fire from a group of former players who have launched a class-action lawsuit in a Minnesota court seeking damages for head injuries they suffered during their playing careers. Multiple attempts by the league to have the players' lawsuit dismissed have failed.

In his letter, Blumenthal makes a reference to a series of e-mails, unsealed by the Minnesota court back in March, in which Bettman, deputy commissioner Bill Daly and Brendan Shanahan, then head of the league's player-safety department, appear to acknowledge a link between fighting, head injuries, concussion and depression, all factors that may have contributed to the deaths of three former NHL players - Derek Boogaard, Rick Rypien, and Wade Belak - in the summer of 2011.

Boogaard's father, Len, was quoted by Blumenthal's office, praising him for "an enormous service to this generation of hockey players and the next," and noting that the senator's advocacy "helps raise public awareness of this issue and leads to answers to these important questions facing hockey."

Blumenthal was particularly anxious to get Bettman to acknowledge the link between contact sports and CTE - something the NFL did for the first time earlier this year.

"Unfortunately, the NHL's response following the NFL's admission has been dismissive and disappointing," Blumenthal wrote.

"As the premier professional hockey league in the world," the senator added, "the NHL has an obligation not only to ensure the safety of your players, but to also engage in a productive dialogue about the safety of your sport at all levels - from youth to professional."

Some of Blumenthal's questions will be easier to answer than others. For example, he asks the league to outline the process by which a player is disciplined for an illegal head shot.

Much of that information is available on the NHL's own website, in the explanations of supplementary discipline matters.

He also asks for details on the current protocols for diagnosing and treating concussions, which the league could manage in a day.

Other queries, however, are more pointed and thus will be more challenging.

With a lawsuit still pending, it is difficult to imagine Bettman will give a definitive response to the question: Do you dispute that the documented CTE of former NHL players, such as Derek Boogaard, is linked to injuries sustained while playing in the NHL?

Bettman is not believed to be under any legal obligation to respond, but for a handful of the easier queries, it wouldn't be out of character for him to provide long, detailed responses, so that he can outline, for the public record, exactly what steps the NHL has taken since 1997 to reduce the incidence of concussions in the game.