Police and the city medical examiner are investigating the death of a human fetus that was recovered Monday night from a rest room at Kapolei Regional Park.

Investigators estimated the developmental age of the fetus, a female, at about 30 weeks.

They said a female who appeared to be in her late teens was complaining of stomach cramps and went to use the rest room just prior to 9 p.m. She gave birth while using the toilet, police said.

The woman denied knowing she was pregnant, police said.

Bryan Cheplic, spokesman for the city's Emergency Services Department, said paramedics were called to the park at 8:51 p.m. and took the woman to a hospital in serious condition.

The fetus was pronounced dead at 9:50 p.m., Cheplic said.

The approximate gestation age of the fetus will be determined at autopsy, police said.