A "mysterious" disease that kills patients within 24 hours has claimed at least 18 lives in a southeastern Nigerian town, the government said Saturday.
"Twenty-three people (were affected) and 18 deaths were recorded," the Ondo state health commissioner, Dayo Adeyanju, told AFP.
The government spokesman for the state, Kayode Akinmade, earlier gave a toll of 17 dead.
"Seventeen people have died of the mysterious disease since it broke out early this week in Ode-Irele town," Akinmade told AFP by telephone.
The disease, whose symptoms include headache, weight loss, blurred vision and loss of consciousness, killed the victims within a day of falling ill, he said.
Laboratory tests have so far ruled out Ebola or any other virus, Akinmade said.
The World Health Organization meanwhile said it had information on 14 cases with at least 12 dead.
"Common symptoms were sudden blurred vision, headache, loss of consciousness followed by death, occurring within 24 hours," WHO spokesman Tarik Jasarevic told AFP by email, adding that an investigation was ongoing.
Another WHO spokesman, Gregory Hartl, told AFP that according to a preliminary report, all those affected began showing symptoms between April 13 and 15.
Akinmade said health officials and experts from the government and aid agencies, as well as WHO epidemiologists, had arrived in Ode-Irele to search for answers.
The state's health commissioner, Adeyanju, told AFP that he and his officials had gone on a "field visit with the WHO, UNICEF, NCDC (Nigerian Centre for Disease Control)".
"This was basically a case search to unravel the cause (of the disease)," he said in a text message.
The WHO's Jasarevic said blood and urine samples had been taken from two victims and cerebrospinal fluid from another.
"All samples have been sent to Lagos University Teaching Hospital this morning, and results are still pending. Investigations are still ongoing," he said.