LUDINGTON, Mich. -

Volunteers are back in the woods to search for plants that could solve the mystery of a missing baby in northern Michigan.

The Ludington Daily News says searchers fanned out in light rain about 8 a.m. Saturday in Mason County's Grant Township. The effort began Friday.

Investigators believe seeds and other material found on the shoes of Katherine Phillips' father could be crucial to the location of the body. The 4 1/2-month-old girl disappeared two years ago from the Ludington area.

Sheriff Kim Cole says volunteers with knowledge of botany have been "passionate" about helping authorities. The goal is to collect certain plants that might help police eventually find Katherine's remains.

Sean Phillips has not been charged with the girl's death but is in prison on a related conviction.