The body of a teenage girl who may have been a runaway was found Friday in a neighborhood near Tysons Corner, authorities said. In an apparently unrelated incident, a body thought to be that of a 91-year-old man was found in a lake in the Reston area.

The girl’s body was found in the 8200 block of Madrillon Estates Drive, Fairfax County police said. Officers were “looking for a reported 16-year-old runaway,” police said. They said the body was found about 11 a.m.

The cause and manner of death remained to be determined, police said. They said the investigation was continuing.

Madrillon Estates Drive is a cul-de-sac west of Gallows Road and south of Tysons. A neighbor said she had been told that the girl lived elsewhere in the county.

In the other incident, police said they were searching Friday morning for an elderly man whose property had been found in the 11100 block of South Lakes Drive. While searching, police said, officers found a body in Lake Thoreau, next to a shopping center.

Police said Friday night that they thought the body is that of the 91-year-old man they had been looking for.

The investigation was continuing, police said, but the death “does not appear criminal in nature,” they said. The location is east of Reston Parkway, about a half-mile south of the Dulles Toll Road.