LEFLORE COUNTY, Miss. — A Marine Corps transport plane plunged into a soybean field in the Mississippi Delta, killing 16 service members and scattering fiery debris far across farmland and a rural highway, the military confirmed on Tuesday.

Among the first witnesses at the scene of the crash, which happened Monday afternoon, was David Habig, a crop-duster pilot who flew over the wreckage. “Lo and behold, all I see are bodies out in the bean field,” he said. “They were everywhere. It was horrific. I’d never seen anything like it.”

The plane was a KC-130 belonging to a Reserve unit, Marine Aerial Refueler Transport Squadron 452, or VMGR-452, nicknamed the “Yankees” and based at Stewart Air National Guard Base in Newburgh, N.Y., the Marine Reserve said on Tuesday.

The flight, which took off from Marine Corps Air Station Cherry Point in North Carolina, was headed to Naval Air Facility El Centro in California and was transporting personnel and equipment, the Reserve said in a statement. There were 15 Marines and one Navy corpsman aboard.

Six of the Marines and the Navy corpsman were assigned to the Marine Raiders, an elite special operations force. They belonged to the Second Marine Raider Battalion, based at Camp Lejeune in North Carolina, according to Maj. Nicholas Mannweiler, a spokesman for the Marine Corps Special Operations Forces.

Major Mannweiler said the Raiders were scheduled to conduct “routine” training in Yuma, Ariz., lasting a few days to a couple of weeks, for small teams preparing for deployment overseas. He would not comment on when or where they were to be sent, but the Raiders are assigned to Central Command, which conducts operations in the Middle East, South Asia and Central Asia, including Afghanistan and Iraq.

The military did not immediately identify the dead. “While the details of the incident are being investigated,” the Marine Corps said in a statement, “our focus remains on providing the necessary resources and support to the family and friends of these service members as they go through this extremely difficult time.”

The crash occurred around 4 p.m. in Leflore County, between the small towns of Moorhead and Itta Bena, about two hours north of Jackson, the state capital. Mr. Habig, 60, said he was flying at the time and got a call from the sheriff’s department asking him to go to the site to check out reports of an accident.

“They were getting calls that something was on fire,” he said. “I don’t think they knew it was going to be that bad.”

Mr. Habig said he flew at 500 feet, maneuvering around a thick black column of smoke rising from the flames, and then descended to…