NELSON COUNTY, Va. (WRIC) — As the investigation continues, new details are being released in connection to a business jet that crashed in mountainous terrain Sunday afternoon in Nelson County.

According to authorities, a Cessna Citation 560 — a turbine twin-engine aircraft — took off from Elizabethton, Tennessee, and was headed to Long Island McArthur Airport in New York. During the flight, the airplane became unresponsive, prompting F-16 fighter jets to be deployed from Joint Base Andrews in Maryland around 3 p.m.

The FAA originally reported that the plane crashed around 3:30 p.m. on Sunday afternoon, however, a defense official told ABC News the crash occurred closer to 3:50 p.m. According to ABC, the fighter jet interception occurred around 3:20 p.m. approximately 20 miles northeast of Reagan National Airport. The F-16s then accompanied the Cessna plane for about half an hour before it crashed. The plane crashed approximately 2-3 miles north of Montebello, Virginia, in heavily wooded and rural terrain.

Hours later, police and rescuers reached the site of the plane crash in the Shenandoah Valley. According to police, there were no survivors found. Authorities said there were four people on board the plane at the time of the incident. The aircraft’s owner, John Rumpel, reportedly told The New York Times that his daughter, 2-year-old granddaughter and nanny were on the plane.

NTSB official says long investigation ahead

There are now three different agencies conducting different investigations of the incident — the Federal Aviation Administration (FAA), the National Transportation Safety Board (NTSB) and Virginia State Police. NTSB Senior Air Safety Investigator Adam Gerhardt spoke with reporters on Monday morning about the investigation’s progress.

“The accident site will take us extensive time to get to,” said Adam Gerhardt, the lead investigator of the crash for NTSB. “The wreckage is highly fragmented … I want to stress that we are in that preliminary fact-finding stage. So, at this point in the investigation, the most important aspect is … to look at the perishable evidence. What I mean by that is that with the passage of time, it is going to get a lot more difficult to collect that information.”

The NTSB investigation will cover the airplane, the engines, the weather conditions, the pilot’s qualifications and the maintenance records, among other areas of focus. Gehardt also said his team would be analyzing the avionics on board to try and determine when the pilot became unresponsive and why the plane took the flight path that it did.

“This airplane was not required to have a black box or a cockpit voice recorder or a flight data recorder,” Gerhardt said. “But we’ll be looking at whether or not that equipment may have been installed.”

A preliminary factual report will be released by the NTSB within 10 days. However, the final report is expected to take anywhere between 12 months and 24 months to be released.

“We expect to be here for at least three or four days,” Gerhardt said. “The wreckage will be recovered [helicoptered] to a secure facility in Delaware … It will be a very challenging accident site.”

Sonic boom heard over Washington DC

North American Aerospace Defense Command (NORAD) Continental U.S. Region reported that authorities were concerned about an “unresponsive ” plane flying a strange flight path over the D.C. area Sunday afternoon. F-16s were scrambled to investigate which led to a sonic boom that was heard over the D.C. area.

NORAD reported that the F-16s used flares in an attempt to draw the attention of the pilot.

“Flares are employed with highest regard for safety of the intercepted aircraft and people on the ground,” a release from NORAD read. “Flares burn out quickly and completely and there is no danger to the people on the ground when dispensed.”

A White House official said President Joe Biden has been briefed on the incident.