Federal authorities were investigating Monday what caused a private jet to fly into restricted airspace over Washington, DC, on Sunday, triggering a response from military aircraft that sent a sonic boom being heard across much of the region before after the little plane crashed in Virginia. , killing all four people on board.

The private commercial plane crashed near Montebello, Virginia, the National Transportation Safety Board said. A Virginia State Police spokeswoman said in a statement Monday that emergency services were able to reach the wreckage on foot about four hours after receiving a report of a plane crash.

John Rumpel, who runs Encore Motors of Melbourne, a Florida-based company that owns the plane, said in a phone interview Monday that his daughter, Adina Azarian, her 2-year-old granddaughter, their nanny and the pilot were on the plane. . and did not survive.

The plane, a Cessna 560 Citation V, crashed “almost in a straight line and at high speed,” he said, adding that the impact caused a crater and debris spread for 150 yards. Mr. Rumpel had said on Sunday that they were returning to his home in East Hampton, New York, after a four-day visit to his home in North Carolina.

Two fighter jets were dispatched from Joint Base Andrews in Maryland after the Cessna entered restricted airspace, prompting the emergency response to intercept the flight, US and military officials confirmed Sunday.

After the Cessna veered into the restricted area, which includes major national landmarks, the Federal Aviation Administration called the pilot but received no response from that plane, and the military ordered the planes to intercept, a military official said.

The North American Aerospace Defense Command, or NORAD, which oversees US and Canadian aerospace control, said in a statement that two F-16 jets were deployed Sunday after the Cessna flew over Washington and northern Virginia. .

NORAD said the fighter jets “were authorized to travel at supersonic speeds,” which would have produced the roar heard in the region, including suburban Virginia and Maryland. The planes also used flares that may have been visible from the ground, the agency said, “in an attempt to get the pilot’s attention.”

Officials later determined the Cessna did not pose a threat, and the investigation will look into why the pilot did not respond to the FAA. The Cessna was not shot down, officials said. A White House official said that President Biden was briefed on the incident.

The Cessna crashed near the George Washington National Forest in Virginia, NORAD said, though an earlier FAA statement said it “crashed into mountainous terrain in a sparsely populated area of ​​southwestern Virginia” near Montebello around 9:00 p.m. 3:30 p.m. local time.

Adam Gerhardt, an NTSB investigator, told reporters Monday that the agency would be on the ground for at least three to four days. He said the remains were “highly fragmented” and described the area as rural and mountainous.

“It will be a very challenging crash site,” he said.

Gerhardt said the investigation would look into exactly when the pilot became unresponsive and why the plane flew the route it took. He said it was not yet known whether the plane had a cockpit voice recorder or a flight data recorder, though he said the aircraft was not required to have such equipment.

“Everything is on the table until we slowly and methodically remove different components and elements that will be relevant to this security investigation,” Mr. Gerhardt said.

Rumpel, who is also a pilot, said Sunday he had little information about the circumstances of the crash, but hoped his daughter, granddaughter and others on board had not suffered. His voice cracking, he said that if the plane lost pressurization, “everyone would have just gone to sleep and never woke up.”

“It was going down at 20,000 feet per minute, and no one could survive a crash at that speed,” Rumpel said.

Ms. Azarian, 49, worked as an agent for Keller Williams Points North, the real estate company, in New York City and Long Island. The company said in a statement Monday that her death was a “profound loss” to her colleagues and family.

The plane had taken off from Elizabethton Municipal Airport in Elizabethton, Tennessee, and was headed to Long Island MacArthur Airport in Ronkonkoma, New York, the FAA said. The Cessna left Tennessee at 1:13 p.m. local time, according to the FlightAware flight tracking website.

The Annapolis Office of Emergency Management had also said on Twitter that the sonic boom was the result of an authorized Department of Defense flight.

People reported on social media that they had heard a loud bang throughout the Washington area. Many said the noise sounded like an explosion, and some said the rumble was so loud it shook their homes. TO sonic boom it is caused by an object moving faster than sound, or about 750 miles per hour at sea level.

Rafael Olivieri, 62, said he was at his home in Annandale, Virginia, when he heard a “very brief, loud sound” that shook his house. Mr. Olivieri ran outside, where his neighbors were also trying to find out what had happened. “The first thing I did was look at the sky,” he said. “I was really worried.”

More than 30 miles to the northeast, in Edgewater, Maryland, 47-year-old Joseph Krygiel also felt the boom. He said he was in his basement shortly after 3:00 pm when the entire house trembled. “It felt like a big thing,” Krygiel said.

derrick bryson taylor and mark walker contributed reporting.