The families involved live in towns about 75 miles apart on opposite sides of the Blue Ridge Mountains. The other mother in the case, Paula Johnson of Ruckersville, Va., approached the hospital two weeks ago with DNA evidence proving that the 3-year-old she had been raising, Callie Marie, was not her child. Ms. Johnson had sought DNA tests to establish the paternity of Callie's presumed father and to induce him to make child-support payments.

Marguerite Beck, a spokeswoman for the hospital, said the hospital had suspected that the switch was not an accident and had called in the Virginia State Police to aid in an investigation. She said the hospital had not yet named ''Family B'' -- which Mrs. Watts says is her family -- as Callie's biological parents, but that it had dispatched a physician and a nurse to visit Family B.

The families of Mr. Chittum and Ms. Rogers, who are caring for Rebecca, have sought seclusion while they grieve over those killed and arrange custody of Rebecca and the 1-year-old daughter of Mr. Chittum and Ms. Rogers, who were engaged.

The two mothers presumably involved had known each other.

''I remember Whitney from the hospital as a warm and enthusiastic person,'' Ms. Johnson said in a statement today through her lawyer, Cynthia A. Johnson, who is not related. ''For the last few days, my life has been an absolute nightmare with reporters stalking me, Callie, and members of my family.

''I am looking forward to the chance to meet with the other families and my biological daughter in private,'' she said of Rebecca.