One of Russia's richest women, S7 Group co-owner Natalia Fileva, died Sunday in a plane crash in Germany, the airline operator said.

Fileva, 55, was aboard a single-engine, six-seat Epic LT aircraft that crashed and burned in a field as it approached the small airport at Egelsbach, a town in southwestern Germany, at about 3:30 p.m., the airline said in an email.

German police said there appeared to be three people aboard the plane, including the pilot of the flight, which originated in France. They said the two passengers were believed to be Russian citizens but that positive identification of the occupants would require further investigation.

German aviation authorities were probing the cause of the crash. Egelsbach is about six miles south of Frankfurt.

The business publication Forbes.ru estimated Fileva's fortune at $600 million.

"S7 Group team extends sincere and heartfelt condolences to Mrs. Fileva's family and loved ones," the company said in a statement. "The memory of her as an inspiring and sympathetic leader and a wonderful person will forever stay in the hearts of all S7 Group employees. It is an irreparable loss. "

With a base at Moscow's Domodedovo Airport, S7 is part of the Oneworld alliance and flies to 150 destinations in 35 countries, using 56 Airbus planes and 23 aircraft from Boeing. Fileva's husband, Vladislav Filev, is listed as chair of the company's board of directors, according to the company's third-quarter 2018 financial statement on its website.

Two other people died in a traffic collision related to the plane crash. The dpa news agency, citing police, reported that a police vehicle that was responding to the plane crash was struck head-on by another vehicle. Three police officers were seriously hurt, while both occupants of the other car died.