A newly signed death certificate says an accident killed a 21-year-old Green Bay woman found dead in her submerged car this summer, but police are still investigating the case.

Brown County medical examiner Al Klimek signed the document yesterday after his review of the death of Mahalia Xiong.

Her relatives suspect foul play. They've suggested someone might have spiked Xiong's drink with a date rape-type drug when she was out with friends before she drove away and disappeared in July. Her body was found two weeks later inside her car in the Fox River.

Klimek confirms that Xiong had small amounts of an anti-seizure medication in her bloodstream when she died. He says the drug is usually prescribed to treat convulsions, but it wasn't prescribed for Xiong.

But he also notes that an autopsy found she was over the blood-alcohol limit for driving when she got in her car. Klimek says the main thing that could have prevented the death was if she had decided not to drive.

The investigation by Green Bay police is continuing.