Girl's Body Found; Transient Arrested

Police have found what they believe is the body of a 6-year-old suburban St. Louis girl who vanished from a kitchen this morning, prompting a massive, all-day search.

"We found what we believe to be the body of Casey Williamson in an abandoned glass factory a little bit south of here," said St. Louis County Police Chief Ron Battelle. "Her body has not positively been identified, but we believe it is her."

Under arrest was Johnny Johnson, 24, "a local transient" who was staying in the Valley Park, Mo., house with Cassandra "Casey" Williamson, Battelle said.

Formal charges had not been filed, but the chief said Johnson had made a statement and was cooperating.

"It appears as though he was the only one involved," Battelle said.

He said an autopsy would be conducted to determine the cause of death.

Last Seen in Kitchen

Before the body was found, about 100 people, including volunteers, local police and the FBI, had been searching the area with helicopters, boats and bloodhounds.

Casey's father last saw the little girl in the kitchen of the house where they were staying before 7 a.m., and she was reported missing to police around 7:30 a.m., said Sgt. Bob Frohne of the St. Louis County Police, which handles police duties for Valley Park, about 20 miles southwest of St. Louis.

The Williamsons and their four children were staying overnight at a house across the street from their own home, Frohne said.

The Associated Press reported the father, Ernie Williamson, lived there with a roomate because he was separated from his wife, though the entire family often stayed there, as they did Thursday night.

Casey's mother, Angela Williamson, said her husband left Casey in the kitchen and went to the bathroom, but when he returned, the girl was gone.

"He woke me up and he asked me where Casey was," Angela Williamson told ABCNEWS Radio. "I was like, 'I don't know. The last time I seen her, she was sleeping in the back with you.'"

The family and police went door to door in the neighborhood, but turned up no trace of the girl, a police spokeswoman said.

‘Unemployed Fellow’ Interviewed

As the search continued, Frohne said police were interviewing "an unemployed fellow [who] spent the evening on the couch in Cassandra's family home." He apparently referred to Johnson, who police later said had spent the night in the house with the Williamsons.

Police picked up the man in the neighborhood, near the Meramec River, which was searched, Frohne said.

The Associated Press quoted Ernie Williamson as saying the man went missing around the time Casey disappeared and turned up later dripping wet, explaining he went for a swim in the river.

ABCNEWS' Michael S. James contributed to this report.