TRENTON, N.J. (AP) _ A woman told authorities Monday that she threw her housemate's missing 7- month-old daughter into the Delaware River, but police said they didn't know whether to believe the retarded woman.

Divers aided by tracking dogs searched the chilly river for the blue-eyed infant, who disappeared Sunday from a row house near Trenton State Prison. At dusk Monday, the search was suspended indefinitely.

The 30-year-old woman was in police custody Monday but had not been charged, said police Sgt. Robert Orlowski.

When police first questioned her Sunday, the woman said a man had knocked her down, kidnapped the toddler and driven off, Orlowski said. Then she said the man tossed the baby into the river. After further questioning, she said the baby fell off her lap into the river, Orlowski said.

''She admitted this morning that she threw the baby in the river yesterday,'' Orlowski said.

''They don't know really whether to believe her or not because of her diminished mental capacity. She has the capacity of a 4- or 5-year-old. Her story has changed so many times since she reported it, they really don't know what to believe,'' Orlowski said.

''The detective who has been with her all day yesterday and today feels pretty certain this is what happened,'' Orlowski said.

According to police, the woman asked the baby's mother, Rebecca McGuinn, for permission to play with the baby Sunday morning.

Ms. McGuinn gave her approval, but said the woman had to remain in the living room. However, the woman apparently took the child from the house while the mother was asleep, Orlowski said.