WICHITA, Kan. (AP) — Police in Wichita, Kansas, are investigating after a woman found the remains of a human fetus inside a small box along a river.

The fetus was found Sunday afternoon. Police believe it to be 10 weeks gestation or younger. A coroner will examine the remains for a more exact determination.

At a news conference Monday, police Capt. Brent Allred said a 57-year-old woman was near the Arkansas River when she saw a box on a sandbar. Officers were called and found the fetus inside. Bloody towels and other materials also were found in the box.

The remains were taken to a forensics lab for an autopsy.

Police say they have not classified the case as a criminal investigation, pending autopsy results.