Three Marines who were found dead in a privately-owned vehicle parked outside a convenience store in Hampstead, North Carolina, on Sunday, died from carbon monoxide poisoning, according to a release from the Pender County Sheriff's Office.

The North Carolina Office of the Chief Medical Examiner on Wednesday performed autopsies on the three bodies and determined the deaths were "consistent due to Carbon Monoxide Poisoning," the release said.

On Sunday morning, the sheriff's office received a call regarding a missing person, the release said. The caller said her son, a Marine stationed at Camp Lejeune, had failed to arrive on a flight to Oklahoma the night before.

The woman told law enforcement she had spoken with a supervisor in her son's unit and that someone was en route to Hampstead to see if they could find the missing Marine.

Later that morning, the sheriff's office was informed that the missing person, as well as two other Marines, had been found dead inside of a vehicle parked at a Speedway convenience store, the release said.

The Marines were identified Tuesday as 19-year-old Lance Cpl. Tanner J. Kaltenberg, 23-year-old Lance Cpl. Merax C. Dockery and 23-year-old Lance Cpl. Ivan R. Garcia, according to a release from the US Marine Corps.

Brig. Gen. Michael E. McWilliams, commanding general of the 2nd Marine Logistics Group, extended his "deepest sympathy and condolences" to the family, friends and colleagues of the three Marines.

"Our focus is providing the necessary resources and support to those impacted by their tragic loss as they navigate this extremely difficult time," McWilliams said.

Hampstead is about 17 miles northeast of Wilmington and about 40 miles south of Camp Lejeune.