MONROVIA, Liberia (AP) — United Nations officials say at least nine people have died from a mysterious illness in Liberia, and all tests have been negative for the Ebola virus.

The World Health Organization said Friday that authorities are looking into whether the people were sickened by something they ate or were exposed to a chemical or bacteria.

Eight others remained hospitalized in Sinoe County, about 250 miles (400 kilometers) outside the capital, after complaining of abdominal pains.

The cases over the past week have evoked painful memories in Liberia, where more than 4,800 people died during the Ebola epidemic.

Those who fell sick this week all had attended a relative's funeral. That was how many Ebola victims contracted the disease when they came in contact with victims' corpses.