Jeff Myers of the Hoquiam police said citizen tips led them to the young birth mother and her boyfriend. They are now being questioned by detectives.
Myers said the birth took place at a motel in Ocean Shores. Detectives are now at the motel waiting for a search warrant.
The newborn infant's body was found by a woman who was walking with her dog in the 200 block of Fisher Avenue NE at about 6 p.m. Friday.
She noticed a rag hanging from a branch in a wooded vacant lot, and when she walked over to investigate she found a dead baby on the ground, Myers said.
Police responded, and spent much of the next morning gathering evidence and taking measurements at the scene after a break in the weather.