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Sixteen service members were killed in the military plane that crashed Monday afternoon in rural Mississippi, spurring an intense search for bodies and a federal investigation into what caused the fiery wreck.

Marine Corps Maj. Andrew Aranda said at a news conference Tuesday that there was no immediate evidence of foul play.

Investigators are "looking at the debris and we'll be collecting information off of that to figure out what happened," he said.

The flight was part of the Marine Aerial Refueler Transport Squadron 452 (VMGR-452) based in Newburgh, New York, Aranda said. The passengers — 15 Marines and one Navy foreman — had left Marine Corps Air Station Cherry Point in North Carolina and were on their way to Naval Air Facility El Centro in Southern California.

A defense official had earlier confirmed that there were no civilians on board when the KC-130T slammed into a soybean field in Leflore County, Mississippi.

The Marine Forces Reserve said that the squadron was transporting personnel and equipment to California. Aranda, however, could not say if there was any known issues with the aircraft.

"We have some of the best maintainers in the world," he said of the crew that oversees the aircraft. "I trust my life to those guys numerous times."

Fred Randle, the county's director of emergency management, said in a brief phone interview with NBC News on Monday that the search for bodies would continue Tuesday.

Randle said that he had been told that all 16 people aboard the flight were believed dead and "most, but not all" of the bodies had been recovered.

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Related: KC-130 Aircraft Has History of Use During War

Randle had also told reporters at a news conference Monday that the area around the crash site was unsafe due to the presence of fuel.

The FBI was on scene, along with a number of other state and local emergency first responders and investigators, he said.

The Marine Corps released a statement Tuesday that said the “cause of the crash is unknown at this time” and that “the incident is under investigation.”

The statement continued: “The identities of the service members whose lives were lost in this tragic accident are being withheld to allow time for their loved ones to be notified.”

President Donald Trump tweeted Tuesday that the crash "is heartbreaking."

Marine Plane crash in Mississippi is heartbreaking. Melania and I send our deepest condolences to all! — Donald J. Trump (@realDonaldTrump) July 11, 2017

Meanwhile, first lady Melania Trump also expressed on Twitter "my deepest sympathy to all of the military families who lost their loved ones."

The official Twitter account of the U.S. Marine Corps stated Monday that a "mishap" had occurred on a KC-130 transport aircraft.

Andy Jones said he was working on his family's catfish farm just before 4 p.m. ET when he heard a boom and looked up to see the plane corkscrewing downward with one engine smoking.

"You looked up and you saw the plane twirling around," he said. "It was spinning down."

Jones said the plane hit the ground behind some trees in a soybean field, and by the time he and others reached the crash site, fires were burning too intensely to approach the wreckage. The force of the crash nearly flattened the plane, Jones said.

Smoke and flames rise into the air after a military transport airplane crashed in a field on July 10, 2017 near Itta Bena, Mississippi, on the western edge of Leflore County. Jimmy Taylor / AP

Two U.S. military officials told NBC News early Tuesday that the plane flew from North Carolina. An earlier report from NBC affiliate WMC-TV said the flight was out of Memphis. The flight crashed near a highway north of Jackson, scattering debris on both sides of the road, indicating a possible mid-air explosion.

WMC-TV quoted an unnamed state trooper as saying the plane was full of ammunition, forcing responders to be extremely cautious. "We just don't know what it'll do," the trooper told the station.

Marcus Banks, the fire chief of nearby Greenwood, told the Greenwood Commonwealth that debris from the plane was scattered in a radius of about 5 miles, The Associated Press reported.

Vice President Mike Pence tweeted Tuesday that he and his wife, Karen, were "praying for the families of the Marines who lost their lives."

Mississippi Gov. Phil Bryant also asked for prayers for the crash victims and their loved ones in a brief statement. "Our men and women in uniform risk themselves every day to secure our freedom," he said.

Meanwhile, a message posted on the National Guard Twitter account Tuesday read: “Our thoughts and prayers are with the families and friends of those lost in the July 10 @USMC KC-130 plane crash in Leflore County."