(WASHINGTON) — Federal officials have launched an investigation into how an unresponsive Cessna aircraft flew into restricted airspace in Washington, D.C., triggering the launch of fighter jets.

A loud sonic boom could be heard throughout the D.C. region on Sunday as two F-16s launched from nearby Joint Base Andrews in Maryland to investigate, military officials said.

The National Transportation Safety Board said late Sunday it had begun an investigation into the crash. Investigators are expected to be on the ground on Monday.

The unresponsive plane, a Cessna 560 Citation V, traveled at 34,000 feet through restricted airspace before crashing n a mountainous area of southwest Virginia at approximately 3:30 p.m. local time. The Virginia State Police will identify the victims.

The private jet had been owned by Florida-based Encore Motors, The New York Times reported Sunday.

When Times reporters reached Encore’s 75-year-old owner, John Rumpel, he reportedly identified four people who had been on the downed flight: his daughter, a granddaughter, a nanny and a pilot.

Six F-16s from three different units and bases were involved in tracking the Cessna, according to U.S. Northern Command. All six scrambled at the same time.

The two F-16s from the 113th Fighter Wing that took off from Joint Base Andrews were the first to reach the Cessna, Defense officials said. The pilots and aircraft were with the D.C. Air National Guard.

The four other F-16s that scrambled were from the 177th FW from Atlantic City, New Jersey, and the 169th FW from McIntyre, South Carolina, officials said.

“Based on the length of the flight path the FAA described for this event, it is normal procedure to have made NORAD aircraft available at several locations,” a North American Aerospace Defense Command spokesperson said on Sunday.

A preliminary report from NTSB investigators is expected within three weeks, officials said. That report is expected to look at “the human, machine and environment as the outline of the investigation,” NTSB officials said.

“At this early stage of an investigation, NTSB does not state a cause but will provide factual information when available,” the board said.

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