Police have arrested a 37-year-old father in the death of a 7-month-old baby boy found burned in the family's backyard fire pit.

Federal Way police spokeswoman Cathy Schrock said Tuesday the father was being booked into the King County jail for investigation of first-degree manslaughter. She did not immediately identify him.

No formal charges have been filed.

Schrock says the father originally told police he fell asleep late Saturday with the boy on a bench near the fire pit. He said that when he awoke the baby was gone; the boy's body was found in the fire pit covered with burns.

When police were called to the home early Sunday, Schrock says officers found the father holding the lifeless child.

The King County medical examiner's office says it won't release the cause of death until Wednesday.