The Marine Corps cargo plane that crashed in Mississippi, killing 16 earlier this week, appears to have suffered a mid-air failure, according to a senior Marine officer.

Brig. Gen. Bradley James, commander of the 4th Marine Air Wing told reporters during a news conference in Leflore County, Miss., that there were two impact sites roughly a mile apart.

“Indications are, something went wrong at cruise altitude,” James said. “There is a large debris pattern.”

Marine and law enforcement officials are working to preserve both scenes for evidence collection, he said.

On Monday evening about 4 p.m. local time, air traffic control lost contact with the four-engine aircraft, a KC-130T from Marine Aerial Refueler Transport Squadron 452. Shortly after that, the plane crashed near the town of Itta Bena in western Mississippi.

Residents on the ground told local news stations and the Associated Press that they heard a boom and looked up to see the aircraft tumbling out of the sky with one of its engines aflame. The plane went down in a rural area of soybean fields and low lying vegetation. Fires from the wreckage burned into the night.

The Newburgh, N.Y.-based aircraft — call sign Yankee 72 — was carrying 16 service members including six Marines and one sailor from the elite 2nd Marine Raider Battalion and nine crew members when it went down. All aboard were killed. The aircraft was ferrying the team of Marine Raiders from an airfield in North Carolina to predeployment training in Yuma, Ariz., and was also carrying the group’s small arms and accompanying ammunition.

The KC-130T is one of the older variants of the aircraft by the Marine Corps. It can be configured to refuel aircraft in midair in addition to being a general purpose cargo and personnel transport. It is based off the C-130 Hercules, a Cold-War era stalwart that has appeared in every American conflict zone since Vietnam.

Following the crash, more than a dozen agencies have responded to the scene and surrounding countryside, James said, including personnel from the FBI, Bureau of Alcohol, Tobacco, Firearms and Explosives, and Homeland Security Department. Military bomb disposal technicians were also dispatched to deal with possible unexploded ordnance among the debris. The FBI is not leading the investigation, a Marine official said, but was on the scene to help with recovery efforts.

The service has yet to release the names of the dead as it is still in the process of notifying next of kin.

The incident is the deadliest aviation accident for the Marine Corps since a 2005 helicopter crash in Iraq that killed 30 Marines and one Navy sailor. The Yankee 72 crash also marks the latest blow to the tightknit Marine Corps Special Operations community. In March 2015, seven Marine Raiders from the 2nd Raider Battalion died when the Army helicopter they were riding in crashed off the Florida Panhandle, killing all 11 aboard.

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