LUDINGTON (WWJ/AP) – Authorities are seeking plant experts to help find the remains of a West Michigan baby who disappeared nearly two years ago.

Ludington police said Wednesday they plan to search in late June using botanical evidence found on the shoes of Katherine Phillips’ father.

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Michigan State University scientists, working with a global expert, have identified an extremely rare seed of sedge that is only found in a few locations in and near Ludington. Also found were algae, pine, dune sand and moss — which, all combined, should considerably narrow down the search area.

Sean Phillips was sentenced to 10 to 15 years in prison last year for an unlawful imprisonment conviction in the case, which police and the FBI have said they’re treating as a homicide.

Officials say the June 28-29 period was chosen because it’s the same timeframe Katherine disappeared in 2011 and similar plant material will be present.

Ludington Police Chief Chief Mark Barnett said, in a release out Wednesday, that Phillips stated in a letter that he put Katherine in a “peaceful place.”

“Ongoing examinations of the material found on Sean Phillip’s shoes are being conducted in an effort to determine the whereabouts of this ‘peaceful place,'” Barnett said.

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Katherine was 4 1/2 months old when she was last seen. She lived with her mother, Ariel Courtland, in Ludington, about 80 miles northwest of Grand Rapids.

According to Courtland, Phillips told her that Katherine is still alive — but extensive searches haven’t turned up the girl. Police did, however, find her clothing in Phillips’ shorts pocket.

In September, Courtland filed papers in an effort to marry Phillips so she could visit him to seek answers about their child’s disappearance.

Anyone with information about what happened to Katherine is asked to contact Mason-Oceana 911 at 231-869-5858.

Authorities are also requesting that anyone who has documented the flora in the area surrounding Ludington contact Detective Wells at the Ludington Police Department at 231-843-3425.

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