Three Republican lawmakers are questioning the direction and handling of a probe into the death of Navy SEAL trainee Kyle Mullen last year.

Reps. Nick LaLota (R-NY), Morgan Luttrell (R-Texas) and Cory Mills (R-Fla.) expressed concerns of potential bias in the investigation that resulted in Capt. Brad Geary being informed that he would face non-judicial punishment in relation to Mullen's death.

“It has come to our attention that the Navy’s investigation into Seaman Kyle Mullen’s death has potentially been misdirected and mishandled,” the lawmakers wrote in a previously unseen congressional inquiry written in June that was obtained by the New York Post on Sunday (September 24).

“We are concerned that, if true, the US Navy’s actions could serve detrimental to our nation’s warfighters at a time when we face grave threats to our national security,” the group added.

Mullen, 24, died in February 2022 after completing his Hell Week training from acute pneumonia and cardiac arrest, according to a military investigation obtained by NBC News on October 12, 2022. The investigation, which was completed by the Naval Special Warfare Command Line of Duty, ruled that Mullen succumbed to illnesses in the line of duty, rather than because of the military branch's own misconduct.

However, the Armed Forces Medical Examiner's autopsy report, which was included in the Naval Special Warfare Command Line of Duty investigation, also found that Mullen's heart was more than twice the normal size at the time of his death in February 2022 after an electrocardiogram hadn't yielded any abnormalities nine months prior.

Medical experts have provided varying arguments on whether Mullen's enlarged heart was caused by the grueling training or the potential use of performance enhancing drugs after drug paraphernalia was discovered among his possessions after his death.

Mullen had just completed the fourth week of Basic Underwater Demolition/SEAL (BUD/S) training, commonly referred to as Hell Week for its notorious difficulty, at the time of his death on February 4, 2022.

The training session has Navy SEAL candidates go through courses intended to simulate intense combat situations, which includes training in harsh environments, swimming in cold bodies of water for long periods of time and going through sleep deprivation.

Mullen had previously attempted to finish BUD/S in the summer of 2021, but suffered a heatstroke during his first attempt.

Only an estimated 250 of the 1,500 Navy SEAL candidates who enter Hell Week training annually complete the training session, the Navy stated via NBC News.

Three Naval officers were reprimanded in connection to Mullen's death, according to the Naval Special Warfare Command Line of Duty report via the Associated Press.

Commanders didn't directly blame the officers for Mullen's death and no terminations were made, however, the incident led to notable changes in how sailors are monitored during training.