Police on Monday identified two small children found dead in Alsea Bay last week and said the siblings recently had moved with their parents from Michigan to an Oregon coastal town.
The parents, Christian Michael Longo, 27, and Mary Jane Longo, 35, and a 2-year-old sister, Madison, were missing.
Zachary Michael Longo, 5, was found floating in the bay Wednesday. His sister, Sadie Ann Longo, 3, was found three days later by divers, according to the Lincoln County Sheriff's Department.
"We don't know what's up yet," said Lincoln County Dist. Atty. Bernice Barnett.
Barnett said the family had moved to Oregon several months ago, but did not have any relatives in the area.
"Something like this that happens in a small town is personal to everyone," said Gary Bessette of Tidewater, a community north of town. "The more I think about it, the more I want to cry."
Police were searching for two vehicles believed to belong to the Longo family.
An autopsy of the boy's body revealed no obvious signs of trauma. An autopsy of the girl's body also was conducted, but authorities did not release the cause of death.
Divers searching the bay for clues Saturday found the girl's body under the bridge opposite the bank of the inlet where the boy was found. Police believe she died at about the same time as the boy and her body appeared to have been in the water since Wednesday.
"Obviously, this is quite a shock," said Lincoln County Sheriff's Lt. Ed Stallard. "It's bad enough to have one child found dead. But now [we] have two, and then apparently some parents that cannot or will not report the children missing."
Investigators said neither child died of natural causes.
Police have considered that a car may have run off the highway and sunk in the bay. Stallard said the theory was unlikely because no skid marks were found on the road and there was no oil slick on the water.
The two children bring to 10 the number of victims who have been found in Lincoln County waters in the last month. Four men died earlier this month when their crabbing boat capsized off Newport, and two teenagers were swept off rocks near Depoe Bay in November.
Earlier this month, the bodies of two people who apparently committed suicide washed ashore in the Newport area.