Fairfax County police are investigating the "suspicious death" of a 15-year-old Chantilly girl whose body was found yesterday several blocks from her home and a block off Route 50.

The body of Rebecca Lynette Reese was found about 7 a.m. by a man walking a dog near a small playground sandwiched among suburban houses close to the Chantilly Plaza shopping center in western Fairfax County. The cause of death was "not readily apparent," a police spokesman said.

About six blocks away, Jonquil Reese, Rebecca's mother, spoke briefly to reporters yesterday afternoon in hushed, almost whispered tones about the curly-haired daughter she said had left the house about 8:45 p.m. Saturday, saying she was planning to meet a friend at the local grocery store.

"She said she'd be back in 20 minutes; she was just going down to the store," the mother recalled. Shortly after midnight Jonquil Reese called police, fearful that Rebecca had run away from home, as she had a few times before, according to county police spokesman Michael Proffitt.

The next word the mother received about her daughter was when police returned to her house yesterday morning with the news: Rebecca was dead; the cause would not be known until an autopsy is done this week.

Proffitt said investigators were interviewing neighborhood residents yesterday afternoon and that the probe was "focusing at this time in the Chantilly area."

Rebecca would have been a junior this fall at Chantilly High School.

A police spokesman said the death was labeled suspicious, rather than an apparent homicide, because "we do not know the cause of death. It's hard to speculate," in part because "there were no marks on her body that would indicate the apparent cause of death . . . .

"We don't want to alarm the public" about the prospect of a killer on the loose, the spokesman said.

As Jonquil Reese flipped through the pages of the family's life history yesterday afternoon, image after image of Rebecca popped up in the photo album: Rebecca at the beach, Rebecca with her head in her hands, blue eyes smiling back at the photographer.

"I surprised her" with the camera, said one of Rebecca's three sisters, standing behind her mother at the door of their well-maintained two-story home on Adelphi Court, a small cul de sac in the Brookfield subdivision. Rebecca also had a brother; family acquaintances said her parents divorced several years ago.

The house has been up for sale. A family acquaintance, who asked not to be identified, said the family had hoped to move farther from the city in search of "more land."

"It's really bothering me -- they're all wonderful kids," said the acquaintance, adding that the Chantilly neighborhood "seems like a safe place to be."

Seven homicides were reported in Fairfax County in the first seven months of this year. Last year, 28 slayings occurred, according to county police.

Police said Rebecca's body was found in a common area behind town houses on Mason Dixon Drive, about half a block from the shopping center and one block from busy Route 50.

Jennifer Gyles said police closed off a small playground area behind Mason Dixon drive and a separate area near her home on nearby Virginia Dare Court for less than four hours yesterday morning before leaving the scene.