A 22-year-old Fairfax County woman found dead in a stranger's swimming pool in Arlington County on Sunday had been at a party about a mile away early that morning, police said yesterday.

Police were trying yesterday to figure out how Megan Criste of Burke wound up in a fenced backyard pool in the Lyon Village neighborhood 14 hours after she was seen at the party. Her body was discovered at 3:45 p.m. by a homeowner heading out for a swim.

Family members said Criste, an outgoing Lake Braddock High School graduate with ambitions of being a photographer, went to a party in Arlington's Lyon Park neighborhood with four friends. Investigators said they have since interviewed guests who saw her between 1 and 1:30 a.m. and said she became separated from her friends before she was discovered hours later in the pool in the 1700 block of North Adams Street.

Investigators say that Criste's partially clothed body bore no visible signs of trauma and that toxicology tests to determine whether she was under the influence of any substances will not be completed for several weeks. Family members said Criste knew how to swim.

Police said they did not know how long she had been in the water.

"She either went to that pool alone and ended up dead or she met up with other people we don't know about and went to that pool with them," said Matt Martin, spokesman for the Arlington police. "That's what we're trying to figure out."

Amy Uriell, 34, a sister of Criste's, said she was told that Criste had "some type of disagreement" with the longtime friends who drove her to the party.

"Maybe that's why she left the party or didn't leave with them," Uriell said, noting that things "aren't adding up" to the family.

"I think someone is holding back some information," Uriell said. "I can't believe that Megan would hop a fence and jump into someone's back yard and enter a pool. It's just not something she'd do."

Lyon Village abuts the busy Clarendon area, which is packed with bars and restaurants. Residents said yesterday that the area is frequently the scene of after-hours bottle throwing and yelling and people urinating on lawns.

"If this is related to that, people will be saddened but not shocked," said Mark Weinress, president of the Lyon Village Citizens' Association. "A lot goes on. Kids party. It's a tragic thing, but it's also something the restaurant and bar owners need to be watching for, how much their customers are drinking."

Criste and her twin brother were the youngest of six siblings. At the time of her death, she was living at her parents' home in Burke. Family members said that after high school, she was employed as a waitress at Glory Days Grill in Burke, where she worked for several years before waiting tables most recently at Heart in Hand Restaurant in Clifton.

Uriell said Criste was particularly fond of photography and enjoyed writing and drawing. She said her sister was considering going to college, possibly for a degree in graphics design or another profession in which she could use those skills.

"She was a very happy person, very outgoing, very talkative," Uriell recalled yesterday, her voice choked with emotion. "She was very quick-witted. Absolutely gorgeous. Tall, thin, beautiful."

Criste's family members spent several hours yesterday at a funeral home making the arrangements for her service, picking out a coffin and buying a burial plot.

"It's been heart-wrenching," Uriell said. "It just doesn't feel real."

Police and family members are asking anyone who was in the Lyon Park, Clarendon, Courthouse or Lyon Village areas between 1 and 6 a.m. Sunday who might have seen Criste to call Arlington police at 703-228-4195.

Staff researcher Bobbye Pratt contributed to this report.

Megan Criste, 22, knew how to swim, according to her family.