But police say the screw was jammed down the throat of the girl to make the death look like an accident, and that she died because she was beaten and suffocated.
The couple were suffocated by fumes from a faulty gas fire.
A 29-year-old mother told police she suffocated her two young sons before strapping them into their car seats and driving them into a river.
Many suffocated trying to crawl out of the tunnel, Mr. Zhou said. Only three or four survived.
